Hiroshi, the only son, has to live with his stepmother Akari, as his father is remarrying with a woman 20 years younger than him. Although Hiroshi is a recluse who rarely does his job and tends to stay at home, he can't hide his excitement at the idea of living with Akari, who is only 5 years younger than him. One day, while cleaning, Hiroshi's excitement reaches its peak when he sees a glimpse of Akari's panties under her skirt... From that day on, Hiroshi is completely captivated by Akari's seductive charm...