Riko has successful career as an employee of a company. Her brother, Takashi, moved out to go to college and lives on his own apartment. One day, Riko goes to Takashi's apartment while he's not there and comes across an anal porn DVD when cleaning his room. Curiosity overcame her and she began to watch the porn video and masturbate. When Takashi comes back home he catches her in the middle of the act...