Rimu's boyfriend, Ichiro, was worried that he always got a half-erect erection during sex. One day, at the meeting place for a date, he witnessed Rimu being hit on and felt an intense stimulation in his lower body. He realized that he had an NTR desire and asked his best friend, AV actor Kenji, "I want to have sex with Rimu with a rock hard erection!" and decided to have sex with Rimu and cuckold her.