Shota-kun is having fun playing ninja at the park when he meets runaway gyaru AIKA-chan, who invites him back to her place. Then comes a shocking twist—AIKA-chan's older sister and Shota-kun's father were once teacher and student. But their relationship went far beyond that, crossing forbidden boundaries. Seeing a gyaru's ass again after so long, Shota's father begins stroking AIKA's back, leaving Shota deeply shocked. Realizing he must master his own naughty ninja techniques, Shota stares intently at his sister figure's plump, jiggly hips and reaches out to touch. The sensation sends his dick into a full erection, and using his newly discovered ninja art, he ends up pleasuring himself together with the older sister until they both reach blissful ecstasy.