Nana and her friend Go-Chan are searching for the mythical Sagatawa Crystal, which legend has it brings ultimate happiness to men and women who hold it in their hands. They finally find the object, but it makes them switch bodies. Now Go-Chan has Nana's body and will take advantage of it to enjoy the pleasures of her new female body. Finally, Nana discovers a way to return to normal, but the price to pay will be very high.