When she arrives at his house, she sees an ambulance and a police car. The house is old and crumbling apart at the seams, and she can hear yelling from inside the house though she can't make out what they're saying. One of the police officers comes to the tsundere and asks her what her business is and she says that she's come to deliver someone from school's assignments, telling the officer MC's name.
There's an awkward silence for a moment as the police officer struggles to put the situation into words in the least harmful way, but eventually he comes to tell her that MC's going to a crisis center for a suicide attempt, and that he's not going to be in school for a while.
After FMC eventually gets a hold of MC's suicide note, she realizes the internal struggles he's been facing with depression, abusive/neglectful parents, bullying at school, etc. and everything that has lead to his decision. She then begins to reconsider her relationship with MC, trying to learn about him more as a person and reevaluating her feelings for him, and how she never considered what he might be going through, instead kinda focusing on herself as tsunderes tend to do by proxy.
The rest of the series after that is the two working through their own struggles with mental health, trying to support one another. When the Tsundere begins to relapse into her old tendencies, she remembers how MC internalizes his struggles and becomes non-vocal, and she'll bite her tongue and apologize, or when MC's own insecurities and faults shine through, the tsundere has to give in a bit and support him in her own way.
I would want the series to focus on how you never know what's going on inside a person's head, and how people can be seemingly fine or fit in whilst in reality their own circumstances may be absolutely miserable, and that it's for this reason you should try to be nice to everyone. I don't want this to be like Gal Cleaning where it's shocking for the sake of being shocking but because it's using that shock to prove a point about how someone's lack of information and assumptions could lead to unfortunate circumstances.
Plus it would be interesting to pair a tsundere with someone who doesn't react well to it and has their own issues, like what happens in NGE, and seeing how the psychology of the two characters works out.