Kosuke lived alone with his stepmother, Rena. She had been dating a man she liked, but one day he broke up with her, leaving her heartbroken. To comfort her, Kosuke accompanied her on a drinking binge. That night, as Rena became increasingly drunk, she leaned against Kosuke for the first time, and seeing her so close, drinking together, he found himself deeply moved by her feminine charm. That feeling gradually intensified, until he could no longer suppress it.