Mutsumi Mutsu, nicknamed Moo, was a victim of severe bullying that drove her to a mental breakdown. In response, she staged a convincing performance of being possessed by a rumored deceased student named Judas, an act born from her desperation and readiness to drop out of school.

This incident earned her a mixture of respect and fear from her classmates. Mutsumi then used her intellectual advantage to manipulate others into believing ghost stories about Judas, creating a cunning strategy to protect herself from further bullying. This manipulation was not malicious but a survival tactic.

She later extended this protection to Alice, a new transfer student who was ostracized for using Judas's old desk. Mutsumi performed a ritual to banish Judas's spirit, shielding Alice from similar harassment. She eventually confessed to Alice that the Judas story was a hoax, explaining that her actions were intended to stop the bullying and that she viewed both herself and Alice as victims of the narrative.

Mutsumi possesses an original personality with a mature and assertive demeanor. She employs her intellect to control classroom social dynamics, ultimately befriending Alice and demonstrating that her manipulations were rooted in self-preservation, not cruelty.