His virgin brother, who took his sister's provocation seriously, is not aware that he is cumming and runs wild.

Mitsuki teases his popular younger brother as a joke. The virgin brother mistakenly thought he was actually tempted to him and inserted his dick into his sister right after his parents left. Mitsuki has reached orgasm due to the overwhelming momentum, but her younger brother, who is not used to women, continues to shake her hips in a slut. Even after climaxing, she is chased by pleasure from the continued thrusts, and continues to climax, continuing to climax until her parents return home. She completely ignores her sister screaming, "I'm already... I'm cumming!!" and climaxes with her thrusts!