Let's go with Danganropa Uktra despair girl WOH with an oldie but Goldie prompt of having a Depressed(who wouldn't be with their backstory) older sibling reader. The older sibling, despite the things that have happened, has always tried to take care of them/protect them, even if they've failed at times and despite what they're also gone through themselves.
Even though after escaping the hopes peak riot(they're a former ultimate) and the tragedy, they still care for their younger sibling. Even taking care of the other WOH isn't an issue for them since someone has to keep these children alive cause Nagito be tripping with the stiff he does.
Depressed older sibling is always taking care of them
𝆹𝅥 Platonic headcanons
𝆹𝅥 Kotoko Utsugi, Masuru Daimon, Jataro Kemuri, Nagisa Shingetsu, Monaca Towa (DANGANRONPA ANOTHER EPISODE ULTRA DESPAIR GIRLS)
𝆹𝅥 Mention of depression and abuse
Kotoko Utsugui
Kotoko loved her family, she really did, thats why she bared everything her parents forced her to do, still that never stoped herself from being scared, from wanting to run away, to cry her heart out while begging for not letting anyone to be gentle with her again, and thankfuly for her you were there for her!
You have gone throught the same that Kotoko has being experimenting, you have been in her place at her age too and thats why, despite barely being able to keep going with your life thanks to the inmense void that you feel inside of you because of what happened you never left, you found in Kotoko a reason to keep going because you didn't wanted her to suffer, maybe you couldn't stop it but you could be there for her
You became Kotoko's safe space, she always ran and hide in your arms whenever she had to face her parent's plans, whenever it was time for her to be used again or even after, helping her collect the small pieces of her broken heart and get ready to keep going. Even if you couldn't stop your parents, even if you offered to take her place over and over again to try to safe her from this cruelty as much as posible you couldn't stop this completely, so instead you decided to take care of her, to be and actual guardian for her and help her live like the inocent child she was, at least for a moment
Deep down Kotoko always knew that things weren't easier for you and she would be forever greatful for having you in her life, thats why when the plan of taking down the demons was settle she talked to Monaca about you, she told her about how you weren't like the other demons, even if you were a grown up you were a good person! Convincing her to let you live and be at her side before rushing out to try to bring you with her, even if she had to spend sleepless night until she managed to find you she will, she will not rest until you are back to her side
Once you finally were at her side Kotoko clinged to your side for several days, never leaving you and passing from thanking you in tears to proudly tell you what she have done to your parents (hopefuly you won't get mad at her), saying that she finally was able to protect you too!
Even when you started to take care of the rest of the Warriors of Hope (and teaching Nagito how not to poison them accidently) she always left clear that you are her sibling, she has privilage with you and she will always be your priority (along with Monaca), that even if you are willing to take care of everything she is your favorite! And she will constantly going to you side, trying to get your attention and showing off how she is better that her friends (specially from Masuru since they already have a rivality)
Kotoko request for you to share room with her, she will never admit it to the other Warriors of Hope but she can't sleep if you aren't at her side, it wouldn't be the first time nor the last one, after all she is too scared to wake up and finding her parents again, to be told to be ready since she has a performance to do, and if that happens at least you will be there for her like you always did
Monaca Towa
Monaca always tried to be a good child, she wanted nothing more than be accepted by her family even when everyone limited themselfs to just interact with her when necesary and looking at her like the pest they see her as, everyone except for you. Despite everyone hating her you were always kind to her, giving her the attention and the aprovation she craved for, wich quickly made her attached to you, clinging to your side and always trying to make you smile, wanting to make you prideful of her so you could give her the affection she craved for, you were like heaven for her!
Monaca is really smart and observant, it didn't take her long to realice that you weren't alright, that despite always having a smile for her, kind words and the gentle care she wanted so much you weren't fine nor happy, even if you tried to hide it or even don't know it yourself she quickly realices that you were suffering from depression and just as quick she made her personal goal to take care of you! You were her only real family and she wasn't planning to leave you suffering all alone!
You two grow so close to each other that it felt like you two just needed each other, there was no need for anyone else, but Monaca was angry to the rest of the family, who not only treated her as a pest but also push you on your limits enough to fall in depression, so after meeting big sis Junko she took the oportunity without hesitation, after all she would built a world were you could be happy too!
Monaca felt bad for you to suffer when she started to use the wheelchair or to be colateral damage after taking down Towa City but in her plans it wasn't to leave you all alone, you were the only grown up that weren't a demon so she would keep you close! Her plan was to keep you at her side from the start but if while taking down the city you would get lost Monaca would throw a tantrum until any of the Warriors of Hope or Monokids found you and bring you to her (although, this time her tears were real, she wouldn't admit it but she was scared of losing you)
Once you are safe and sound with her she would tell you with the brightest smile that you have nothing to worry anymore! She had everything under control and you could finally be happy, truly happy! You would be able to keep taking care of her like you have always did because now she could offer you a home where she will be taking care of you too!
In all honestly, Monaca really hopes you can be happy now, she want to see you smiling at her forever and she is working hard to try to save you from your depression the way she thinks it will help, she feels a bit jealous that you started to take care of the rest of the Warriors of Hope too along with Nagito but she can see that this is helping you, you were feeling happy and at peace, you take this new place as your true home (and she made sure she would always be your priority), and if they make you happy then she won't mind sharing you a bit, it has always being just the two of you and it would always be that way, but right now at least you two don't have to deal with horrible people who used to wish no of you were born
Masuru Daimon
For Masuru you were like a super hero! Ever since he can remember you were always at his side, acting like an actual guardian and doing everything in your power that he could grow up as a happy child, shielding him as much as posible from your father and always doing what he asked so non of you got in troubles, and thats the reason why you became his hero and the person he admired the most!
Masuru never understood the extent of your depression, he could see that you were hurt and sad but because of the circumstances you two live in he thought it would be because of it, once he grow up enough to understand better the situation he decided that he didn't liked it so he tried his best to be a good brother, always trying to make you happy in any way posible, whenever you two had time to just hang out he was always trying drag you to play, always showing off and talking a lot about how amazing you were, how he wanted to become like you when he grew up
Eventually Masuru started to understand the real gravity of not only the life you two are living but the burden in your shoulders, growing to appreciate even more than despite being hurt, scared and probably exhaustated you always managed to take care of him with a smile, thats when Masuru took more serious everything and decided that now he wanted to be your hero! Just like you were for him!
When he accepted to be part of the plan of Monaca and big sis Junko he did it with you in mind, if he, along with the Warriors of Hope, take control over the city he would be able to become a hero! He will be your hero! So, as the leader of the Warriors of Hope he launched the plan in no time
He didn't say anything about the plan to you but promised that everything would be alright, that he will make sure of it, so when they finally took over the city and until they were in control he searched for you because it was until that moment that he could truly be your hero, and he want you to be proud of him!
He talked a lot to the rest of the Warriors of Hope about you, you were a hero and even if you were a grown up you weren't a demon, so, as the leader, he expect all to welcome you with open arms (it didn't happened exactly like he wanted but at least you were at his side again), he never planned to bring you to take care of all of them, after all he wanted to be the one protecting you now, but it just happened, after all they are still kids and don't really know how to take care of themselfs
Despite the fact that you and Nagito are the ones who are taking care of all of them Masuru always insist that now he is your hero and that he is the one taking care of you (just because he wants to feel like he could do that for you too, he will be upset with himself if you say thats is not true), and despite being incredibly competitive he won't mind much sharing you as long as you keep telling him that you are proud of him and keep playing with him as always
Jataro Kemuri
Your mother has always had a problem with you two, maybe i was just the anger for having to take care of you two or the envy of how beautiful her child actually are you two were always treated like monsters
Jataro has probably being if not already so close to fall into depression as you too, however the fact that you are at his side is comforting enough, since you were treated the same way by your mother you somehow managed to convince Jataro that you too are a monster, looking at him without the mask won't have any effect on you since you two are the same, being able to give hin some time to rest of that thing
You were all Jotaro had, despite how much your mother words affected him you managed to slowly heal those wounds in your own way, quickly becoming the safe space of each other and where you two could just be, you didn't had to pretend to be fine for his sake because he accepted your depression as it is, but also by knowing how bad you actually were he wanted to take care of you too, even if he couldn't do as much for you as you do for him he still tried his best to be a good brother and try to make you happy (a bit motivated by his own desesperation)
Jataro was hesitant to go with the Warriors of Hope, after all for him you were the only thing he needed but he was convinced by the idea that maybe this way he could do something to make you truly happy! Besides, he would not be able to stop them and if he doesn't go he won't you probably got lost or even worst. After taking care of your mother he imediatly went with you, almost begging you to go with him because if you don't go then he won't neither (altought, since he is already convinced that this is a good idea he will end up having a crisis if you don't want to go)
He introduced you to the Warriors of Hope personally and for once he fight them to defend you, yeah, you were a grown up but you definetly weren't a demon! You were just like him and you are everything he has, without you he won't work with them! At the end there was no room to object and you stayed with them
As he have always been Jataro was incredibly clingy, now that is not just two to of you but also the rest of Warriors of Hope and the servant and because of that he was constantly in he edge, scared anytime you leave his side because you are the only one who truly matters for him, he didn't wanted to share you no matter how much you wanted to take care of the others too, it took a lot of reasurance (and kinda showing him that Nagito wasn't the best to take care of all of them alone) when he finally allowed you to look after the others, still that didn't stopped him from clinging to your side whenever he could
Nagisa Shingetsu
For your father you two have been nothing but subjects for his experiments, ever since you were a kid you were subjected to intense study sesions, your life was completely made to have the best grades and accomplish all your father asked, but no matter how well you did he would always ask for more and for better results
Your whole childhood was waste by his experiments, when you least expected the exhaustation and deep sadness that grow inside of you quickly made dificult to keep with your father's rythm, making it more and more dificult to get the results he wanted before he simply left you alone and turn to your little brother, making him take your place now that his results were better, trying new and better methods with a complete new test subject
Your inside was a complete mess, the feeling of being a complete failure and self-hate was more present than ever after being push away, but despite the despair and even the great void inside of you there was a part of you that just simply couldn't let your father make Nagisa go throught this, you couldn't let him ruin your little brother's life too
Somehow you manage to prove some more use while supervising Nagisa's improvements and studies, after all you gave him enough good results to prove that you won't just mess with his project, taking advantage of the little freedom and trust you gained to take care of Nagisa as much as you could, trying to sneak anything you could for him that could be of use to give him a break from the stressful study sesions, even if it was just a bit of food and water
Despite how much Nagisa tried to avoid it at first, fearing that he would make his father angry, at the end he accepted once he realiced how much you were actually doing for him, not only risking while sneaking things for him without your father's knowledge but also fighting the deep burden in your heart, he was smart enough to conect the dots and notice how bad you were feeling, how whenever you expressed concern for him it wasn't pity or because you underestimate him but rather sincere concern and self experience, so he decided that he would work harder, to get even better results just to prove to you father (but most important, to you) that your presence was of great help and an amazing influence
Once the Warriors of Hope decided to take the city Nagisa found out a way to include you in the plan of the Warriors of Hope, finding a way to make it seem like you were an important part for the plan before rushing to find you, using everything in his power and not resting at all until you were at his side again! He wanted to act mature, he wanted to prove to you that he was stronge and smart enough to take care of everything! But the fact that you two were finally free and the fact that you were finally able to treat him as your precious little brother (to hug him and take proper care of him) quickly break his facade, clinging to your side and crying his heart out after you two meet again
The fact that you end up taking care of not only him but the rest of the Warriors of Hope gives him mixed feelings, for one side he is incredibly relieved because now they want you here too, it makes him happy seeing you happy for being with so much kids (that actually act like kids) but in the other side it makes him feel jealous, he hates it and deny it as much as posible but he can't stop himself from either looking away or clinging to your side (the last one is mainly when is just you two)