nagi was spending every day devoted to idol training at a training school. one day, her parents said they would be away from home for a few days and left, leaving her alone with her brother yuzuru. yuzuru is an otaku and looks at his sister nagi with special feelings different from their brother-sister relationship, and engages in perverted acts such as secretly filming her panty shots so that nagi doesn't notice, and licking the mouth of the juice his sister drank, treating her as a sexual object. taking advantage of the fact that his parents are not home, yuzuru's perverted acts escalate... my only flesh masturbation idol sister, seduced by nipple development and big dick appeal.