Fumika lives with her mother and stepfather. Over time, the stepfather unknowingly observes private moments of his stepdaughter and becomes increasingly fixated. His suppressed desires escalate to the point where he can no longer restrain himself, and he confronts Fumika in the bathroom, a place beyond his wife's vigilant gaze. Despite Fumika's initial resistance, he persists, touching her in an attempt to "bond" with her, and ultimately forces himself upon her. Unexpectedly, Fumika begins to experience a woman's pleasure in their sexual encounters.
