Maki is a married female teacher returning to work after maternity leave. However, on her commute, she unexpectedly becomes the victim of a molester. Though she volunteers to keep watch over the students, her unsatisfied forty-year-old body quickly succumbs to the molester's skilled fingers. Making excuses that she's doing it "to protect the students from being touched," she becomes obsessed with the secret pleasure during her daily commute. Before long, Maki awakens to the shame and pleasure of being groped in crowded trains. And once again today, she boards the train as usual, ready to experience a new development.