After attempting to jump off the roof of her high school building, Azusa miraculously survives. Her relief is short-lived, however, when a group of people in eerie masks abruptly take over the school. In a disturbing turn of events, the group kidnaps a pregnant teacher and causes the sudden disappearance of the principal and male students. Amidst the chaos, Shigeo, a fellow classmate, hands Azusa a perplexing envelope filled with fragments of a secret crucial to unraveling the school's bizarre predicament. Fueled by a desperate need for answers, Azusa follows Shigeo and eventually stumbles upon a mind-bending revelation.
