Nao, a country girl comes to Tokyo after graduating from university. Because she couldn't find a job and didn't have a house, she went to stay at her sister's house. However, every time the night comes, she is bothered by her brother and sister's sex. Because she was a teenage girl, she was extremely curious about it, so when her sister was away from home, she dressed only in sexy lingerie and rushed to her brother-in-law who was sitting on the chair reading the news...