Onimata Kan is famous for two things: a successful career writing S&M erotica, and hosting the erotic gatherings aboard what has come to be known as the Slave Ship, where the main attraction is the auctioning of the services of sexual partners willing to fulfill any desire. So if it's all consensual, there's no harm, right? At least, that's what Onimata believes until he learns that one of the frequent auctionees has gone insane, and that her husband believes the cause is related to a stalker she acquired. Are the activities aboard the Slave Ship somehow to blame? Fearing the answer, Onimata goes to investigate the mysterious Kitagawa, and soon learns that his own writings only hint at the extremes to which some will go.

Kaori Yumiko is a high school girl with large boobs and a track athlete. One day, she is hit by a car and seriously injured, but her life is saved by surgery performed by Dr. Osuga. However, Yumiko's breasts have been transformed into a peculiar condition where they become huge when she gets excited! Using the power of her gigantic breasts, she wins the track and field championship. She quickly becomes a beautiful busty idol star, but then another super busty idol appears who persistently harasses Yumiko. In fact, this idol is a member of the evil busty army "Ura Mespai"! And Dr. Osuga is none other than the head of the Japanese branch of "Mespai," a secret female organization fighting for world peace. Now the final battle between Ura Mespai and Mespai has begun!