Chihiro transfers into Ryouichi's class, reconnecting after years of lost contact as childhood friends. She remains ignorant of his childhood brain injury sustained during their play. Upon discovering his condition and the incident's consequences, Chihiro feels profound guilt. This guilt drives her to pledge unconditional assistance to Ryouichi. He manipulates this vow, demanding sexual acts from her. Though reluctant, Chihiro's conscience binds her to the agreement, forcing compliance. Her submission becomes integral to Ryouichi's revenge scheme, targeting those he deems responsible for past wrongs by transforming women into his personal sex slaves.