Himari Kosaka's relationship with her company supervisor gradually deepens. Although she's gone as far as oral sex before, she's never had full intercourse. Using her work mistakes as an excuse, her boss begins pressuring her for penetration. During her first real sex, when her cervix is hit, Himari convulses and squirts uncontrollably, transforming into an extremely sensitive, lustful woman. Her reaction is so intense, as if her instincts have run wild, completely taking over her body and mind.