Minamo Nagase used her skills and charm to seduce Daisuke, her sister Arisu's boyfriend. One night, while Daisuke was sleeping in bed with Arisu, Minamo sneaked in to tempt him. Daisuke couldn't resist the allure of Minamo's large breasts and her skillful techniques, so he was seduced by her time and time again. And then Arisu found out and had a "showdown" with Minamo to find out who could make Daisuke feel better!