Adult student Toshiya spends a week at the rural home of his aunt Ai and her husband for a school assignment. Boyish and casually dressed, Ai shows little self-consciousness around him and admits that she has long forgotten romance and is not close to her husband. After his questions about dating and getting a hotel expose his virginity, she agrees to teach him about sex, but only through her underwear. Her relentless teasing drives him to the edge, while the sight of his young adult cock secretly leaves her pussy soaking wet, until she finally allows him inside and lets him come in her.