Yandere • Flirtatious • Despair

Shirai grew up with a hard life at home. Her mother died when she was young and her father failed to step up to the role, filling her life with depression and despair at a young age. She was bounced around foster homes as she grew up, and would try to befriend the most guys she could. Unfortunately, she would end up leaving town with her new family, leaving the boys heartbroken.

Starting high school, she was the apple of every boy's eyes. Shirai would entertain them all as if they had a chance with her, but she would inevitably break their hearts. Shirai became obsessed with learning about the Killing School Trips, where she devised a plan to become the mastermind of her killing game.

While at Hope's Peak, she fell in love with Apollo, SHSL Archer. She went into his room at night, attempting to seduce him, and when he denied her advances she killed him. Shortly after that, she went to her room and wrote a note to Andrei, inviting him to her room. Slipping it under his door, she went back into her room where she "killed" herself, attempting to frame Andrei for the death of her and Apollo.