A defenseless, busty sister gets fucked by her super-strong younger brother. She thought she was seducing her virgin brother, but... it turns out to be a surprise!

Chitose, who works at an apparel shop in Tokyo, has taken advantage of the long weekend to return to her parents' home. However, when his younger brother Yota, who doesn't show up, became worried and asked his parents about it, he found out that he had been dumped by a girl and hadn't gone to school. In that case, Chitose tries to cheer up Yota by showing off her huge braless breasts in order to get her interested again, but she awakens the abnormal sexual desire she has been sleeping with, and is chased by her super-strong younger brother, who looks like a monkey, and is constantly fucked...