An otaku college student who started living alone when he entered college. Envying such a man, my sister began to enter and exit the room frequently. One day, my brother's friend and my sister ran into each other. A sister who seduces him, who is as shy as his brother, with a panchira and enjoys his reaction. My sister, who enjoys teasing the older man, gradually escalates her behavior and destroys her friendship with her brother. My younger sister, who has awakened to an abnormal propensity, will involve even her older brother and seek mental pleasure.