Manji, who is always being teased by the bully Hideo, fell and got hurt today because of Hideo. Then Hideo's sister Yui came to his rescue and gave the dirty Manji a bath. And Yui was naked too! Then Manji ended up staying at Hideo's house. It seems that Yui's boyfriend is also there... What is the precocious Yui doing? ? Just as Manji was dozing off from the exhaustion of this thrilling experience, Yui came into his room...