The fourth installment features the voluptuous, aggressive girl Azusa Ayano and the seductive, luscious-lipped Arisa Kanno. Ayano harbors a secret: a large, vividly protruding penis between her legs. One day, Kanno visits Ayano's home and discovers this secret. Rather than rejecting it, she embraces the sensation of a union beyond male or female, and the two proceed to insert a double-headed incest rape dildo into each other's vaginal openings, as the female teacher and schoolgirl indulge in an endless, shocking pursuit of pleasure.