It's Takopi's character analysis time because I absolutely refuse to live in a timeline (wahaha. sorry) where the story is divided among viewers between "whose in the right" instead of it being a story about the effect childhood abuse has and how it reflects and repeats in children. And how often children, rather than associate the source of their abuse within their abuser, instead blame outside sources for their abusers actions because a) the abusers place the blame on their actions elsewhere so the children follow suit, and/or b) because the abuse comes from someone the children are supposed to trust with their well being so the children are unable to understand the abuser is acting that way because of the abuser's own faults.
So let's start with child Marina; her parents likely had faults and issues before the situation with Shizuka's mother. We see in the flashback how the father had these suspicious calls the mother was upset about (birthday scene), how he became more detached from the family life (the video games at the table and the mother being annoyed), and how the mother was scolding Marina while holding a video game (taking out her anger at her husband onto Marina). It was subtle, but there. This is a family that has always had problems. The only difference was it wasn't as in the open as it was before, so Marina wasn't aware of how things escalated. From her perspective, everything was perfectly fine, and then suddenly everything exploded when Shizuka's mom entered the picture, making it very jarring for her.
Her father doesn't really want anything to do with Marina or her mother, rejecting the family life entirely. I think he started a family simply because that's what was expected of a conventional life, but he never really grew up emotionally to deal with that sort of commitment, stuck in his "bachelor" days. He continued to behave like that until it all came to a head, and he left the family, thinking nothing of how it would affect the child he began to resent. He barely interacts with Marina post the situation with Shizuka's mom, leaving Marina entirely in the hands of her mother. Her mother, in turn, is responding to this situation in perhaps the worst way possible. Opposite of the father, she's clung hard to this ideal family life, and having the father ruin that caused her emotional instability and denial. Unable to push her anger and frustration in any meaningful way to her husband, she instead turns it to her daughter, using Marina as both an outlet of her suffering and someone to echo back her internal mantra of "you did nothing wrong". Marina's mother very easily turns to physical violence due to her self victimization and being unable to see herself as anything but being wronged. And Marina's father, while not violent on purpose, is shown to be incredibly careless and defensively apathetic to any physical or mental harm he puts on Marina. So Marina is left with needing to respond to her mother's constant state of unstable and dangerous victimization, causing her home to no longer be a safe place, and yet her mother bullies her into coming home sooner rather than later. Marina being on "her mother's side" has turned into a necessity for Marina's wellbeing and survival.
And again, from Marina's perspective, this was all a very sudden change. Everything was good, and suddenly, everything is terrifying, and she can't understand it. But what she does understand, was the big thing that caused her parents to split up in the first place, and that was likely first brought on by Shizuka's mom. Marina is a child, and she loves her mother, so she can't comprehend the concept of her mother's actions being in the wrong, and just focuses on the survivalist mindset of wanting the abuse to stop, while laying the blame somewhere else. So in her mind, if her father would just come back and stop seeing Shizuka's mom, that would stop the abuse. Every time she sees Shizuka, she's reminded of her abuse, therefore attaching the blame of her suffering onto Shizuka. This, throwing one's own frustration towards someone onto someone else, is a learned behavior she's picked up from her mother; Marina's mother can't take it out on the dad so she takes it out onto Marina, Marina can't take it out on Shizuka's mom (or fight back against her own mother) so she takes it out onto Shizuka. And it's with a certain vigor, because she still has this hope that her family will go back to normal. She thinks maybe if she is enough "on her mother's side", or if she blames and hurts Shizuka enough, her dad will come back and everything will be normal again.
As for child Shizuka, she is someone who has always had a lonely and largely unmonitored childhood. While Marina and Naoki's problems stem from the actions of their parents towards them, Shizuka's problems come from the lack of actions from her parents to her. From a very young age Shizuka is left to her own devices, made clear by both of her parents that they have no interest in her or the things that happen to her. Sure they probably have food in the fridge and leave her money if they can, but otherwise Shizuka is basically left to raise herself. As a result, she is left very unsocialized, unable to properly communicate or connect with others because her parents never taught nor do they try to connect with her. When her dad left, she was likely very young and unable to really remember and properly acknowledge his neglect being the same as her mother's, instead more so associating him with the dog he didn't care to bring with him. Chappy is the only living being that is happy to be around Shizuka, becoming the only positive living influence in her life. However, as a dog, he is unable to help her with proper human connection. She is extremely emotionally and socially underdeveloped.
It's likely that Shizuka's existence came from some sort of one night stand from her parents from her mother's work, and they only stayed together due to the expectation that they should. But in practice, neither of them wanted Shizuka and they didn't put in the effort to once she was actually born. The marriage likely ended up falling apart when the father started getting the idea that the mother "trapped" him, rather than it being a decision they both agreed on, much to Shizuka's mother's anger, both at the implication and the loss of income that he was taking with him that she and Shizuka needed, requiring her to work even longer hours, further putting Shizuka into her neglect. Simply put, absolutely no one has ever attempted to meaningfully interact with this child. Shizuka never had anyone that would willingly help her when she'd need it, never had anyone that would take into consideration her desires and wants. This has made her unable to expect this level of care from others to be naturally given to her, nor is she able to properly understand the relationships other people can have with each other. Because she thinks nobody will ever care about her, she's also closed herself off from the idea of wanting someone to care about her, choosing not to chase it and keep it buried.
She also is unable to imagine much about the far future. Being someone that has had to put into action her own needs, such as getting herself food, making sure she attends school, getting anything she needs and so on, her survival has relied on her own self sufficiency. This required her to think in purely next steps. And secondly, she never had anyone to encourage her to become someone in the future. She's a child from a low income household, and has been marked by poverty from the other kids and adults she interacts with, with her baggy clothes and unkempt appearance. She's been the victim of more passive bullying from her peers and blatant apathy from adults when her bad situation is so obvious. She's already been blatantly written off by society as someone who won't ever become anyone, and her parents have done nothing to convince her otherwise. Because of all this, her thinking tends to be very short term, based around what she thinks is necessary in that very moment.
Then Marina comes into her life. Marina bullying her is probably the first time someone has ever given her any sort of vapid attention, and it's an abusive kind. Sure, other kids bullied her, but it wasn't so personal; it was just because she was an easy target. They didn't seek her out so doggedly like Marina does. It's overwhelming and terrifying, and she has no idea how to respond or defend against it. Marina verbally cites her reason for her bullying on Shizuka's mother, but Shizuka, unlike Marina, doesn't assign the blame of her abuse onto another. Shizuka, with her in the present thinking and lack of real bond with her mother, just knows that when Marina's around, she's hurt, and doesn't think too much on reasoning. She, like Marina, just wants it to stop. But Marina's actions just continue to escalate, wanting Shizuka to be just as miserable as she is. She notices that Shizuka loves her dog, and wants to take something she loves away from her. So she does, putting on that whole show and having the dog be put down. Chappy was Shizuka's only positive living influence in her life, and to have that taken away from her was a devastating blow. She's unable to see past it, now seeing nothing good in her life. Her current life was misery, so she decided to take her own life, only for it to fail. After her failed suicide and she and her mother left town, Marina is left to slowly forget about her and Shizuka is left to stew in Marina's actions.
We skip to teen Marina, who has changed a bit from her childhood. She is no longer under any implications that her parents will get back together and everything will return to a state of normalcy. This was likely a slow realization she had to come to when Shizuka and Shizuka's mother left, who she assigned the blame onto, and yet her family and the abuse she suffered remained the same (she likely got the scar around the time Shizuka's mother left, when the mother thought the husband would come back to her only for him to not and to blow up at Marina about it, the physical violence slowly escalating). She still has this violent anger at her situation, but she doesn't direct it towards anyone, leaving her to turn inwards. While as a child she had a group of friends, she now keeps to herself, drawing away from people. And now that she's older, her mother has exploited that and has pushed Marina into more of a "caretaker" role, putting expectations on her like getting her alcohol and such, becoming violent if these expectations are not meant, or citing Marina's behavior as her "no longer caring" about her, twisting her actions to be the fault of Marina's. And her father has stopped being a part of her life all together, only contacting her to "help him out" with her mother and getting her to move on, which she can't do in the first place because of how her mother will react. Her life, in all, is both suffocating and terrifying, with no one around her to help. She's left with fantasies of a life if her mother treats her differently, but as she has given up on a life like that, she instead thinks about how she'll treat her child like that instead.
Then Takopi shows up, and starts constantly following her around. It's the first time she's had a connection outside her abusive mother in a long time, and she doesn't really know how to approach it, mostly outsourcing her built up anger towards him in the beginning. Slowly, she begins to open up to him, as she has no one else in her life to do so with. This is what leads to Takopi, in his limited understanding of humans, having her get with Naoki. And sure, she likes him well enough, they talk for a while, but she likely wouldn't have thought to date him if Takopi hadn't put the idea in her mind. What she likes most about this relationship isn't really a romantic aspect of it, but rather it's having another person to talk to, and the fact that it makes her mother happy. Marina's mother seems to put great value on romantic relationships, so her seeing Marina date someone causes her to sort of live vicariously through this happy relationship, like a do over of sorts. It also allows Marina to not have to go home immediately, having the excuse of having a boyfriend and it being accepted by her mother. So now her mother has reeled back on the abuse, and she's able to hang out with a peer. Marina doesn't necessarily love Naoki, but she loves the way her life is going now that she's with him.
Now here's when teen Naoki comes in. To back up, child Naoki was brought up in a household that valued a purely perfect result and nothing else. An A+? Best in the class? Obviously worked the hardest he could? Doesn't matter if it's not 100%. Naoki's mother is someone who seems to put an immense amount of pressure on herself to be perfect at what she does (saying 'when your a doctor you can't mess up'), and she, like Naoki, had to become this out of sheer hard work (Junya mentioning how she's like Naoki in working hard). And then she had Junya, who can just remember things academically without trying all that hard; a natural "gifted child". When Naoki's mother sees this, she's thrilled; her child was someone she excelled to be all her life, placing all these expectations on him for his future. Then Naoki came along, and the mother, used to raising a child like Junya, expected and was excited for another carbon copy of him. But instead, Naoki, while smart, isn't a natural like Junya academically. Naoki's mother, at this point, has forgotten what it's like to be a child who needs to study, who needs to learn rather than cruise through school. She forgets that she was once like Naoki, and tries to force him into someone like Junya, disregarding entirely the fact that just knowing things without actually trying isn't a common thing, nor can it be taught in a person.
Naoki just has the very natural desire to have his mother love him, and with the father never really being home for as long as he could remember, he's connected all idea of parental love onto his mother. His mother has connected that love with him doing well in school and her pancakes. They're not just pancakes to him, but proof of his mother's love, as she stopped being affectionate towards him after he went into school. But time and time again those pancakes, her love, is pulled away from him no matter how hard she tries, and his mother always cites Junya as the reasoning for this. Because of this, Naoki becomes obsessed with his self worth being tied to what he can and can't do, as what he can't do he thinks is the reason he can never fully get his mother's love. His mother puts so much value in results, in having a good future as a doctor, so that's all Naoki can now see as well, when really he just wants to be wanted. It also causes him to slowly stop seeing Junya as a person, but instead as this unattainable goal and a roadblock to his mother's love. Then the situation with Shizuka, and trying to connect with her when they were little due to a mixture of her being in need of help and her looking like his mother, but Shizuka was unable to see his desire to get closer to her because it wasn't something that has ever happened before.
Then, as teenagers, he met Marina again, remembering her from back in the day as Shizuka's bully. But time has passed since then, and he likely acknowledges her as a different person from back in the day. Teen Naoki is still stuck in the same mindset he's had since he was a child, him desperately seeking his mother's love making him unable to grow past it. But he, like Marina, has lost any idealization that his situation can improve. He's given up the idea that he can take over the clinic instead of his brother, and has given up on ever being "good enough" for his mother. With time, he's completely dehumanized Junya in his mind, thinking of him as just this person whose "better" than him no matter how hard he tries, resenting him for it, growing all the more quietly bitter. When Marina floats the idea of them getting into a relationship, he's not all that romantically interested in her, but he agrees because it's someone that is interested in him, and he's desperate for that. He can't get his mother to want him, so he'll take anyone that comes along. And he never really learned to make deep connections with others due to him being so focused on studying and getting his mother's approval, making him a bit socially underdeveloped and isolated. After, in his mind, if he can't get his mother to like him, how can anyone? So he gets with Marina, and things are mostly the same as ever; till Shizuka comes back to town.
Teen Shizuka has gone through some changes over the years, and it shows physically. She's the only one out of the three kids to have different hair. It wasn't a big change, her hair mostly in the same style, but it's clearly better taken care of, the bangs better cut and the ends of her hair are even. This is likely because she's been cutting her own hair since she was a child, her mother never thinking to, and had gotten better at being self sufficient over the years. When she was away, she hadn't developed much mentally, but understanding emotions is something she grew to understand. This likely came from her understanding of her mother's job, her mother being paid based on the "wants" of her clients. A person's "wants" can affect them so much they'd risk and pay anything to get them. These "wants" have formed Shizuka's limited understanding of how people work. Shizuka has never had anyone who wanted to help or hang around her just for the sake of it, so she thinks if she wants anyone to do something, she needs to play into their "wants" (not in a sexual sense). And what she wants, when she moves back to town, is for Marina to get a taste of what she had put Shizuka through. She took away the only friend Shizuka ever truly had, and she'd never forgotten it. And to do that, Shizuka thinks to take away something Marina "wants", that being Naoki. And she found this to be a rather easy thing to do, as playing into Naoki's "wants" was already centered around her from when they were kids. I doubt she knew what was going to happen to Marina once she'd strung Naoki away, but at the same time, I don't think she would have cared. Rather, I think she would have wanted to fulfill her plan all the more.
I don't think Naoki has a crush on Shizuka in the most traditional sense; after all, he very specifically commented on how "he couldn't prove himself to the girl who looked like his mother". When Naoki sees Shizuka, he sees a more tangible version of "getting love", and he most associates the concept of "gaining love" from his mother, so he developed this desire to be closer to her as a child. And this was fed into by Shizuka having the reputation of having no one who cares for her, being severely neglected by her parents and society. People see her struggling and consistently do nothing. Naoki views this as not having any competition for Shizuka's affections like he had to with Junya. Also Naoki, since childhood, had been conditioned by his mother by this idea that a person can only truly love someone one at a time, limiting his thinking that she can only love Junya or him, depending on results. Shizuka, at this stage in her life, has a more put together outer appearance and a better understanding of human interaction without anyone constantly targeting her, she could go out and make friends. But she chooses not to because she knows that'll better appeal to Naoki. So Naoki jumps at the opportunity to be with Shizuka with his feelings he mistakes for love, leaving Marina behind.
When Marina is dumped, she doesn't so much mourn for Naoki and the relationship they had, but rather the situation she is now put in with her mother. Her mother had finally started getting "better", and now that they're broken up, she fears her mother's reaction. Marina's mother views this break up as Marina's fault, as just another relationship that Marina's mother is unable to hold onto. It's a breaking point for her, the divorce with the father all over again. She puts words into Marina's mouth as she always does, takes it further and further as she always does, and Marina is left scrambling, unable to defend. And, when it seems like Marina's mother was going to kill her, Marina finally physically fights back and ends up killing her mother. It's self defense, but after it's done, Marina is unable to see it that way. Her mother, someone she has always loved despite it all and the one who was supposed to love her, is dead by her own hand. Her mind is scrambling, trying to make sense of it all, and when Takopi arrives, she's looking for anything that could have undone what just happened, reverting to her childlike state of mind of blaming Shizuka, rather than her mother's actions themselves. And Takopi, with his limited understanding of humans and the concept of "killing" and "death", takes this statement very seriously. Here Marina is, crying her heart out, miserable, when all he wants is for his friend to smile, so of course he'll fulfill the request, even though he doesn't understand it, and he goes through great lengths to do so.
So we're back to their childhood state of minds again. Only now, Takopi has come to be involved, approaching Shizuka with his fractured memory. He remembers his goal being something to do with her, and what does he primarily do; make others smile! So that's what he fixates on.
Shizuka, meanwhile, is in the height of being bullied by Marina, and her overwhelming despair worsens by the day because of it. And here is this creature, this harmless presence that will talk to her, so she keeps coming to see him even though she doesn't care for the gifts he provides. In her mind, they are meaningless things that won't improve her current situation. Then, on the night when they're walking Choppy, Takopi expresses his desire, his "want", to see Shizuka smile. Shizuka has no concept of friendship, nor would she understand why anyone would want to see her happy for the sake of this, so this takes her off guard, and can only fall back on it just simply being something Takopi "wants" rather than taking it as any sort of bonding experience. But even with her limited understanding, she's happy that someone has a "want" in life that has to do with her happiness. But then Marina gets Chappy taken away, and Shizuka loses her dearest connection in her life. Now, if she were on her own, she would've just used a rope. But here was Takopi, someone who has been consistently shown to want to have her use his devices, with a rope on hand.
Then comes the whole song and dance of Takopi constantly replaying time, trying to keep Shizuka alive and having no idea how to, nor does he understand the seriousness of any and all abusive dynamics he runs into. In the end, the way he keeps seeing humans handle their problems and coming out on top is through violence, so he follows suit, accidently killing Marina. And Shizuka, in her eyes, never really saw Marina as an individual, but rather a source of abuse, the killer of her one positive connection. So seeing her die, and knowing that from that point on she'll stop being hurt, she's ecstatic, and it's all thanks to Takopi. But alongside that, she never had someone help her to this extent, to care about what's bothering her and take such an active role in trying to make her life better, even though it happened in such a twisted way. So her happiness is genuine, but she also knows Takopi has expressed a want in seeing her smile, and Shizuka still simplifies his reasoning for doing that is his "want". So she makes sure to smile at him, to thank him, to believe in his magic; it's equal parts genuine and her reward for Takopi.
Then Naoki shows up, sees Marina dead. He first thought, as someone who did see Marina as a person, is being horrified at her death, and Shizuka and Takopi's lack of reaction to it. And, unlike Shizuka and Takopi, understands the legal situation side of it as well. But Shizuka, with her short termed thinking and lack of monitored education on the world, hadn't really thought about legal consequences. And even when it's pointed out to her, she can't really see it as anything that bad since she's never really had any big expectations for her future, so going to a juvenile hall isn't as big a worry to her as it is the prospect of not being able to go see Chappy. So Shizuka, what with Naoki already professing the "want" to help her after telling her that turning herself in would lessen her consequences, asks a step further in avoiding legal consequences at all. She doesn't really know Naoki, just telling the truth of her situation, how she has no one, but it has such a profound effect on Naoki, playing into his desires to be the only one that is wanted. Naoki is so conditioned by his mom to perform, so hardwired to succeed to feel like he deserves to live, that he's able to swallow his horror over this murder for the moment. And Shizuka definitely picks up on this "want" of his (as well as when he brings up framing someone else is a good way to avoid the blame). So they hide the body and go into their hanging out era.
The thing with Naoki and Shizuka, is that they're complete opposites of each other in terms of their situations. Naoki's abuse stems from chasing his mother's love, from the unreachable expectations that are put on him. Shizuka's abuse stems from the absolute lack of interest and expectations that her parents have put on her, resulting in her all too clearly understanding that they don't really love her. When Naoki comes to Shizuka time and again, crying about how his mother doesn't love him and only wants Junya, and how Junya is everything he isn't, Shizuka only picks up on how Naoki resents Junya and simply suggests he takes something Junya "wants", since that's her basis for understanding people. She doesn't understand this desire to have his mother love him nor does she understand this pressure to be someone in the future. And when Shizuka presents her clear lack of understanding on how to act in situations and makes morally questionable decisions, rather than truly "help" her like Naoki says he wants to do, he instead does what'll appease her, because in his mind "appeasing" and "helping" are the same thing; unconsciously, he doesn't really view Shizuka as a full individual, but more so what she can emotionally provide for him. Because of their situations and how it's made them develop, it makes them unable to be able to empathize and truly see the other, at least at this stage in their lives.
Then comes Takopi's moral crisis. Here's the thing with Takopi; he comes from a planet without any sort of serious conflict, but the reasoning behind it has morally dubious implications. When he came to his mother, the overseer of the planet, her response to him doing something wrong was to simply have his memories wiped, to start over. This implies that whenever one of her children make a big enough mistake, they simply revert to infants, unable to develop. All the characters we meet on Earth are the way that they are because when things happen in their lives, they aren't able to "start over", they have to move forward. This may have negative effects on them, but they are forced to develop from it, while Takopi and all his other kin are unable to. And Takopi, like the children, reflects this behavior from his mother by trying to solve all the problems he comes across as "starting over" to revert before the problem was even a problem before learning to work through it; with teen Marina and with child Shizuka. Takopi talks about talking things out to resolve issues, but he doesn't actually know how to do it in practice, leading him to have problems with communicating his own feelings and to understand the feelings of others. But here, in this situation with pretending to be Marina and her home life, Takopi is faced with a serious situation and forced to figure out how to develop from this point on.
But back to Naoki, covering up a murder has taken a toll on him, as it would anyone, especially a nine year old. He was able to bury it with Marina, to try and forget about it, but those feelings were all too hard to deny when the body was discovered. He's coming apart, trying to focus on the trip as his last effort to hang onto anything, and it affects his grades. And his mother, while in the same breath acknowledges that he's struggling, instead of asking after him, has declared that he'd given up, and that she will do the same. She'd likely already given up mentally on Naoki for a while now, not able to accept him if he's unlike Junya, and this was just her excuse. And then, at his very lowest, Shizuka proposes that deal. Shizuka, being so emotionally and socially undeveloped, she can only see others in terms of their "wants" in that present moment, behaving more impulsively and less calculated than her teenage self. Her teenage self thought that being manipulative would be the only way she could get anything from anyone in life, but, while she does the same kind of behavior and belief here, Shizuka doesn't really view what she's doing as complex as manipulation as a child. So when the time comes that she's going to go see Chappy is in danger, she takes into account Naoki's current "wants" as she knows them, and tells him that turning himself in would be something that would help her. She doesn't see it as a betrayal, because she only sees the real consequence of being arrested as not being able to go see Chappy, not thinking about things like Naoki's future, nor hers (she also portrays this behavior when Takopi first suggested if this was right and she smiles at him, knowing that's his "want", and tells him otherwise). And Naoki, thinking he no longer had academics or a chance at his mother's love, felt he had no other option but to agree and remain by Shizuka's side. But then Junya stepped in.
Junya, as stated before, is a gifted child, academically speaking at least. School is just easy for him, able to perform well without having to really try. And this is something his mother has always praised him in, while continuously reminding him to study. And he does for a while, but as he realizes he gets the same scores no matter how much he really studies, he doesn't try as hard, doing other things. And he finds that these other things actually interest him more than school, they make him happy. But he can't really talk about them with his mother, since all she cares about are his grades. He constantly feels this expectation from her, that his plan is so set in stone for him, that him thinking of any other path for himself isn't an option. It's suffocating, but rather than quietly drown, he seeks out friends, gets out of the house; he tries to gain his own identity outside of what his mother wants from him, and he finds he likes his life now. But slowly, he starts getting the sense that his little brother is struggling through something that he can't see, and keeps failing to get him to open up about it, until that night. Junya gets Naoki to open up when he feels the most vulnerable, and breaks Naoki's illusions that Junya was something more than human, that he's just Naoki's brother, a person that can be there for him. It allows Naoki to detach from the idea that it has to be one person and nobody else.
So Naoki comes clean, and Shizuka views this not as Naoki choosing not to go to prison, but as his "want" no longer being to help her, writing him off as someone she can no longer play into their wants. In any case, she doesn't really care if people think she killed Marina, since she's about to go see Chappy. But it's not just about Chappy, but her father, and her slight hope that this is a parent that could love her, since Chappy, who was left behind by him, loved her. But when she gets there, he utterly rejects her to her face, claiming that she wasn't even his child, all while holding onto these two new children of his. He looked at her, clearly observing her poor condition, and looked at her like he wanted to turn away, like she was this thing he was embarrassed about. Because he is embarrassed; to him, this Shizuka is just a representation of a past of poverty and being married to a sex worker, which he thought of as beneath him, and he shows this to Shizuka rather than treating her like the daughter she's meant to be to him. It made Shizuka feel dirty, like it was just this confirmation that she was just this unlovable, tainted thing nobody will ever want around. So, as her mind reels, she goes back to what helped her life the first time around, that being violence. If she just performs violence on those kids, maybe everything will be okay. But Takopi, who has been slowly trying to understand conflict, asks her not to. He points out how his devices, while unable to help, would let her find a place away from her misery, and this is all he could do as her friend. And Shizuka, rather than hearing this as Takopi's own version of helping, took this as Takopi's biggest "want" no longer being her happiness, but what he considered to be right. He's no longer someone that she can make help her, so she discards him. And then Takopi remembers.
But now he finds a desire to help both girls, he's found out more about conflict, and he doesn't know what to do. But then Naoki finds him, and Naoki has gone through some changes. His relationship with his brother has improved, but now it's led him to feel guilty about how his actions are affecting Junya. Admitting to covering up that murder has caused his whole family to unravel, and he, someone who has been raised to do everything correctly, can't fix it. But even so, he's been able to mature emotionally due to breaking through that barrier of needing to be perfect, and he helps Takopi sort through his feelings, while also choosing to move on from the whole situation.
So Takopi waits for Shizuka to return, and when she finally does, she breaks down. She's never had cause to yell out her emotions before, because nobody would have cared if she did. But here is Takopi, continuously saying he does care, and she explodes on him. She's begging for help through her violence, screaming for a solution to everything she's suffered up till now, only for Takopi to say all he can offer her is emotional support. And that's when it strikes her; Takopi's desire to have her smile is beyond "want", it's beyond a goal he has, it's a desire to be her friend, to help her through even if he can't. So they stay together the whole day, unable to fix things, but they have one another.
But Takopi isn't done, and he sacrifices himself in a final turn of time.
With Takopi's sacrifice, he isn't able to fully disappear, his ghost haunting the children. His presence encourages positive thinking, it encourages talking through one's feelings rather than turn them into something violent or bottling them up.
It's what encourages Naoki to talk to his brother sooner, and as a result is able to find that support in a way that didn't involve a murder. But more than that, breaking through only seeing his mother's love as the end all be all let him see he had the opportunity to make actual friends all along. He always had people he talked to in school, but he was unable to shift the conversation into anything that would form a real connection due to his singlemindedness. But now, not only does he have Junya's emotional support, he can have others. And it was important for him that he stopped fixating on Shizuka, as Shizuka just represented to him what he could never have with his mother. By letting that go, he let go of needing his mother's support.
As for Shizuka and Marina, due to the ghost of Takopi, they realized they had that little doodle in common. Maybe to them, without their real memories, he was just a character they both imagined. But because of it, and Takopi's subtle encouragement, they were able to find something they had in common, and it allowed them to see the other as an actual person. Shizuka saw Marina's suffering as she sourced out her rage, and Marina saw Shizuka was an actual person and not a misplaced reason why her life was so terrible. They walk home together, side by side, and are able to form an actual connection with each other, one that peruses into their teens. At home, nothing's really changed for the two of them, the abuse is still going on, as evident by their conversation and Marina's scar. But between the two of them and their friendship, they're able to have someone to talk to about it, to have someone be on their side in the terrible situation and help them see the abuse for what it is. To find solace outside of their home lives (which was what Takopi's devices were meant to perform in the first place; a fun distraction). Marina has someone to tell her that what her parents do to her isn't right, and Shizuka has someone who makes her feel like a real person that can socially develop along side someone.
You can't change your abusers, no matter how much you might want to. But that doesn't mean you can't change and develop the relationships you have with others. Those relationships don't have to be your outlet for your trauma, but a place away from it, to grow beyond it. And that's what Takopi's sacrifice did for them, it had them reach out to others, to make friends and not allow the abuse to suffocate every part of their lives like it could so easily do.
