Because of the preparation for the university entrance exam, the younger brother was invited by his older brother's family to stay together for convenience in studying and commuting. Here, he was taken care of very attentively and warmly by his sister-in-law Hatano, but it was precisely because of this that the two gradually developed feelings for each other. The times when the husband went to work were also when their secret affairs occurred. It's a pity that the husband diligently earned money every day to take care of his wife and younger brother without knowing that both of them were cheating on him.