Yamada, a part-time worker who only thinks about butts, has his niece Nanami come to stay at his house. Nanami doesn't listen to what people say and just plays games all day long. Nanami exposes her beautiful butt without any protection... Yamada can't help but bury his face in Nanami's butt... At first he is surprised by this sudden act, but halfway through, he starts to enjoy it and starts to ask for more and more, as if he is toying with her... From that day on, the two of them began a secret relationship.