Okay, I got one.
In this, the main girl (Sae first came to mind when I thought of this) is having trouble sleeping at night because she's sleepwalking. Her roommate comes home and finds her trying to kill herself by cutting her wrist and stops her. She takes some medicine to prevent this from happening again, along with locking up the drawer with the knives, but she sleepwalks again and tries to kill herself by jumping off the roof. Due to these events, she becomes terrified of sleeping and develops insomnia. After three days of no sleep, she's finally reached her breaking point. She unknowingly falls asleep and prepares to shoot herself. She ends up in the hospital, in a coma, until her roommate comes to visit her and sees her awake, walking to the balcony and falling off, dying.
So.......yeah, this is probably the darkest thing I've ever thought of. Please forgive me, Sae-oshis.