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!

Eren, a university student in Tokyo, returns to her parents' house for the first time in a while, but she hasn't been able to talk to her adolescent younger brother and feels a little lonely. One day, she happens to find a erotic book in her younger brother's room, and Eren tries to tease her like she did when she was a child and shows off her huge breasts without a bra, but she awakens her younger brother's lying sexual desire. When her huge breasts were roughly groped and inserted, she was forced to cum inside her one after another, and from that day she was chased by her super-strong younger brother...