One day, while taking a shower, Mikako discovered her brother, a recluse, rummaging through her used underwear. She called him gross and abusive, but he fought back and raped her. Mikako was frustrated but excited by the pleasure of her brother's penis, which she saw for the first time, and gradually became obsessed with the pleasure of his penis as he forced her to have sex with him. Although she hated him, she started to like him.