This game has layers, anyway, my thoughts written in a way I did this for literature class in seventh grade:
1.) While there are hints that perhaps Kotoyuki is a being from an Otherworld kind of thing whisked away to a human world this also serves as an allegory how nobles and rich people are distinct and treat commoners differently. While perhaps in Showa era, things like this aren’t as prevalent in feudal Japan, the story still points out that the Tsunekis build their wealth upon other’s misfortune.
2.) The whole ritual Hinako undergoes before marriage serves as an allegory of a woman discarding her maiden name and being prepared to merge into her husband’s family (the arm replacement seems to indicate she is a part of her husband’s family and no longer just hers — she’s mostly still herself but also carry a weight that is her husband’s family, the crest branding — family crests are common in Japan and often marked onto kimonos, meaning Hinako will be obligated to wear these, and the mask for her to perceive things differently as a wife and a face to the Tsuneki family, she would embrace new responsibilities as an heir’s wife) but these symbols are complex in ways that it could also be interpreted as how Hinako sees herself as a monster, how Hinako feels like she’s losing herself, as well as the burden and trauma she carries from home seeing how her mother treated as a wife, hence why the procession is depicted in the most literal gruesome way.
3.) In relation to the point above, so much of this is tied to Hinako’s struggle for self agency. Being a woman in rural Japan in the 60s, you don’t have much choice. Say Hinako exists two decades after, she might have a better shot by travelling to a bigger town or perhaps attending university. This is your grandmother’s era we’re talking about. Married off to a rich and decent man seems a good enough ticket to escape the horrible life Hinako has at home, and the idea that Kotoyuki might understand her struggles feels like a bargain. She sees that happening for her sister, and while we don’t really know how Junko fares in her new situation apart from Hinako’s own observation that Junko isn’t happy and looking drained after childbirth (which probably influenced by her own fears of marriage), Hinako can’t deny marriage is the only way to leave. Yet, Hinako knows she doesn’t have it to be a wife (people’s remarks of her of how she’s rather boyish, in a sports club, talks back to her father, etc). Hinako also learns the abuse her mom endures at home might indicate she’ll be treated the same. At the same time, she reaches peak power after being turned into the fox monster, seemingly signaling that she wishes to find agency after marriage (perhaps from her newfound status as a nobleman’s wife and societal conditioning). She’s probably conflicted about which part of her actually has more agency.
4.) The game nicely remarks that even marriage to a good man can’t save you if you choose to dwell on trauma. I think this is what the second ending truly implies. Even if Kotoyuki is a man far from what Kanta (or Shu even) is, if trauma keeps Hinako suffering and distrustful, it’ll ruin her anyway. The whole arranged marriage part also enforces this as well. Again, even if Kotoyuki and Hinako genuinely fall in love with each other, the societal pressure that pushes them will make Hinako think the love is a sham and only something she’s conditioned to. I think that’s why we need to track the endings part by part to get the full picture once we reach the True Ending. It’s not that we should erase the concept of love and decide to enter marriage altogether, but it’s about deconstructing what it is about exactly and do we get to choose it for ourselves. “But we have already existed in a time where–”, again, not in 60s rural East Asia. Even today you can still feel the traces of it everywhere and not exclusive to Asia.
5.) It’s right for Kotoyuki to tell Hinako to let go of her past since, well, life moves on, and you do need some closure to yourself that what happened in the past will remain in the past, but it’s interesting due to how mentally scrambled Hinako is, whatever we hear about Sakuko, Rinko, and Shu might just be purely from her point of view/insecurities to justify severing them from her life. Her sister might say something about “leaving her friends behind” that Hinako might twist in her mind too, adding in the “they’ll betray you anyway”. But, since the game does ponder to the complexity of growing up as a woman, sadly it’s based from real social programming in our very reality that for a woman to feel better about herself is to put another woman down, so whatever Sakuko and Rinko feel about Hinako might also be true.
5a.) We seriously don’t know how much of the “gory” things Hinako is doing to her friends is really influenced by Kotoyuki and Junko. I seriously doubt it’s Kotoyuki and Junko. Personal opinions but I think it’s purely from Hinako herself because mental health problems can lead you into some extreme black or white thinking and it’s a painful thing for her to “let go” of something that’s dear in her past. Thus, mentally, Hinako projects it in the most gruesome way, especially with how Rinko and Sakuko truly feel about her. This seems to be a way bride-to-be (fox) Hinako tries to put young (trauma dwelling) Hinako down… which obviously makes things worse.
The boss fights with Sakuko and Rinko could also be interpreted that maybe they both created drama in Hinako's wedding where they finally tell Hinako how they truly feel.
6.) The implication that choosing Shu doesn’t guarantee the best outcome for Hinako; he latches on to the past and the unchanging version of Hinako. Plus that relationship of not wanting to see each other for their gender can complicate things — which might work in today’s society, in some places only though, but not in 60s rural Japan. Shu definitely struggles with how he should treat Hinako. Not to mention that Shu’s solution to “fix” Hinako is to drug her, but the third ending sorta gives us a hint that Hinako in fact can have a choice, although that choice may not be the best (because yanno, Hinako has to choose herself). Choosing Shu might also symbolize the unwillingness to face the future by running away to the unchanging past that in reality no longer works for you (wow, this hits deep if you have nostalgia syndrome).
7.) It’s interesting in ways that to get the True Ending you must unlock as much memory as possible in the Shimizu house. It seems that the first gameplay (and its ending) is what happens if Hinako refuses to take her parents’ genuine regret to account, let her trauma fester, and overdoses herself with pills Shu gives her. As you get to unlock more endings, you begin to be able to piece together the full story. It’s a clever nod to the viewers that “hey, address your trauma and what resolution you can possibly grant yourself instead of just blocking them completely or let yourself be defined only by the rage and grief it caused”. Only then, Hinako earns her full agency. That’s a powerful message I think. This is also a rare case I see in Asian media where seeing generational trauma with empathy is encouraged, but you don't always have to forgive your parents' very harmful actions.
8.) The way this game also calls out parents to not only come to regret the shit they’ve done to their children after they decide to leave the nest. Real shit.
9.) Choice is the driving theme of the story; it seems that Hinako’s feelings for Kotoyuki is actually an independent choice, but again, due to trauma and societal programming, Hinako rejects that she even grows the feelings at all. In ways, Kotoyuki also breaks the convention to his clan’s designs. The "spell" might again, just be societal conditioning that as a man, he must take upon a wife, so he works his ass off to deserve Hinako to the point of losing himself as well, but apparently he grows genuine feelings for her too. If Hinako being the person who rejects her own feelings, apparently Kotoyuki’s independent feelings for Hinako are deemed failure by his family, since perhaps, he courts her genuinely and without deceit. Hence why fox!Hinako faces the Kyubi (Tsuneki ancestors/family who forces her and Kotoyuki into an arranged marriage) and her human self faces the doll controlled Tsukumogami (manifestation of Hinako’s own disgust to herself to actually want good future with Kotoyuki, potentially breaking the cycle, and fear that she might just be stuck in the cycle itself). This is also a clever allegory because the two gods keep opposing each other while holding control over Ebisugaoka. They’re meant to represent suffocating traditions and Hinako being its agent of change.
The True Ending also places Hinako to fully sympathize with Kotoyuki's ordeal. In a way, Kotoyuki probably sees himself as a worthy person only if he becomes a good enough heir to the Tsuneki family and ensures Hinako’s happiness – something of a patriarchal idea of a traditional husband, even though it’s backed by his genuine love for Hinako. Hinako then not only fights for her own agency, but fights for Kotoyuki’s as well. In the True Ending, Hinako actually not only free herself but also Kotoyuki while potentially restarting their feelings as people, instead of a man and a woman to be wed by traditional expectancy, and falling in love again by choice, this time without meddling.
I'll add more if the lightning bolt strikes. Tell me if you wanna add anything. Even there is so much to discuss in one scene alone. Really love this Higurashi-flavored Silent Hill.