Kentarou stays at his aunt and uncle's house during a long holiday. His uncle is away on a business trip, leaving only his aunt, Sumire, and Kentarou alone together. Though nervous and anxious, Kentarou begins to sense something in Sumire's behavior. Without saying a word, she gradually starts revealing her defenseless body, slowly seducing him. Her actions clearly carry a provocative intent, yet she never makes the first move herself. This slyness deeply unsettles Kentarou's heart. His innocent libido eventually becomes uncontrollable and erupts.