One day, Kobayashi receives a parcel at his house. Inside is an adult toy that he doesn't remember ordering. When he checks the addressee, he sees that it is to Rina, the wife of his friend's couple who live next door. Kobayashi has never looked at Rina with lustful eyes, but his wild fantasies begin to grow. Kobayashi visits the Ayana. Rina, who has no idea what is about to happen, welcomes the hungry beast with her usual smile...