Now, if I were to do a game related to a character's mental illness, I'd likely choose Eija Semezou from my Divine Blood setting, and the traditional horror elements would not be an issue for her. Like she'd be perfectly at home talking to ghosts and occasionally booping them on the snoot if they get uppity. She has no problems at all with ghosts. Confused ghosts, she'd just sort of talk to them until they figured things out. Coherent ghosts (typically ghosts that have been around longer in DB) she'd just have conversations with and she'd ask if they want to go through the gate behind her to whatever the afterlife is and some would say yes and some no. As long as the ghost isn't hurting people she wouldn't care whether it's hanging around.

Living people trying to kill her? Not her favorite thing, but she can deal with it. She can and has killed to protect herself or others.

Anything involving combat or the supernatural she's just very fine with.

Now, the horror aspect, the mental illness thing? Let's show her at high school and trying to interact with people. Have it so that you occasionally tap her heart to the side to keep it beating slow and calm. If it starts beating faster then her dialogue options start getting replaced with things like counting the exits or increasingly forceful reminders to herself that X person is not a threat. Have the option to dismiss dialogue options and replace them with something else, but the faster your heartbeat the more likely it is to be her PTSD responses replacing it. Oh, and if someone other than her picks up a knife or something that looks like a knife (say scissors) and she's not actually in combat, have the heartbeat just rocket up and the dialogue just giving things like "Not a cultist." "Not going to be a sacrifice" "Not a cultist" "Not going to be a sacrifice" because at that point she's forcefully locking herself down to avoid hurting innocents.

I'd have one or two people she could interact with safely, like the other main characters and her family, but just keep forcing her into conversations with other people.

Oh yes, this would be made worse because part of Eija's issue is that due to her trauma she "leaks" and people near her tend to be either terrified or else immediately identify her as a threat because everybody can feel her proximity to death. Some people aren't overly affected because they just accept death as a natural part of life and some people might also think that she feels...close to home. So part of her paranoia is whether or not her presence will make the people she's talking to act irrationally. So she might be paranoid that people who shouldn't be a  threat might take a punch at her and she'll have to defend herself.

But yeah, if I wanted to do a examination of mental illness in a game, it would be that...struggling to keep dialogue options to something reasonable. Struggling to keep the mind from imagining horrible possibilities. Trying to force herself to be calm. Trying to deal with being away from her safe places/people.

But conversations with ghosts: that's a safe place. Combat? not safe, but she's familiar with surviving there. Her horror is in dealing with situations where she believes she might hurt someone on accident.


I mean, it would sort of be an exaggeration of my own social anxiety issues.