One of the playable character's alter is depicted mischievously and they used the old term for DID, but i think they got better at writing similar stuff like this overtime
The setting of the game is very grim and a large number of children suffer from it. Due to its gacha nature, quite a few of these children are playable, meaning they are de facto child soldiers. At least seven Operators are children, with quite a few more looking fairly young.
In Chapter 5, although not the loud type, the screen shakes and flashes, showing a gruesome image of an enemy being internally impaled, crystals sticking from the back
Yes. All of the Ursus Self Governing Students are revealed to suffer from PTSD after being the only survivors of an event that happened in their school. Each is shown to have different symptoms and deal with their traumas differently.