Hikari, the younger sister-in-law, heads to Tokyo to focus on her entrance exams. She is warmly welcomed by her older sister-in-law, Maika, but Hikari's gaze lingers lewdly over Maika's body. At first unaware, Maika gradually notices Hikari's increasingly bold behavior. Sensing the shift, Maika grows suspicious, yet the advances do not stop. Her body heats up, succumbing to pleasure, and eventually Maika is completely consumed by Hikari's seduction.