Mio, who was a model in Tokyo, returns to her parents' home for the first time in a while. His parents are happy about the reunion for the first time in a while, but only his younger brother, Jun, seems to be staying at home without going to school. In that case, I tease her by saying, "If you're going to school, I'll let you rub my breasts...", but it awakens her brother's sleeping libido, and she's rubbed her huge breasts roughly and cums inside with childish SEX. It will be done. From that day onwards, she will be chased around all the time by her unfaithful brother.