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!

Sari's younger brother, Ken, is a hardworking student attending a boarding school and was returning home for summer vacation. Sari is in a lonely life, and is delighted when her younger brother returns home for the first time in a long time, and in an attempt to tease her unfeminine younger brother, she says, "My breasts are exposed right now," and she lets her breasts move from behind, but her younger brother's slumber like a wild monkey who has been sleeping until now explodes! A single prank awakens her instincts of superhumanity, and is chased around every now and then to test the knowledge she gained from erotic videos, and is asked to have sex anywhere in the house...