Maki Hojo, a married woman and stepmother, receives little attention from her husband and secretly relieves her pent-up sexual desires through masturbation. Her reclusive stepson has been silently watching her every move through the crack of the door. One day, he becomes intensely aroused when he sees Maki bent over in the living room, wiping the floor with her buttocks fully exposed. Unaware of her stepson's presence, she believes she's alone. Shocked by his sudden attack, she desperately tries to escape, but as he pulls down her skirt and underwear, she grows increasingly confused and overwhelmed.