Ai, a huge-breasted woman whose body shakes wildly as she makes a helpless orgasm face, takes over a public restroom. Bullied by her boss at work and emotionally abused at home, she feels she has nowhere to belong; masturbating in a public toilet becomes her only escape. One day a man enters, and the fear of being discovered awakens her masochistic desires. She eventually offers herself as a public sex toilet, letting one stranger after another use her and fill her with semen.