Momoko Isshiki, a married woman with a strong sense of justice, agrees to help a friend by patrolling commuter trains for molesters. Every morning, she confidently boards the crowded train on her way to work, determined to catch a pervert in the act. But when she lets her guard down, she becomes the victim of a lewd assault—and her long-dormant body quickly begins to respond with unexpected sensitivity. What started as a mission to apprehend a molester turns into a humiliating experience as she finds herself becoming the target. Burdened with guilt yet drawn to the thrill, she boards the packed train once again, heading toward yet another arousing encounter.