A college student otaku boy who started living alone when he went on to higher education. My sister, who envied such a man, began to go in and out of the room frequently. One day, my brother's friend and my sister got into a bowl. - A younger sister who seduces him with panchira and enjoys the reaction as her brother. - Her younger sister, who enjoys teasing an older man who is a shrewd man, gradually escalates her behavior and even destroys her friendship with her brother. - Her younger sister, who has awakened to an abnormal propensity, seeks mental pleasure by involving her brother.