Hiroki, who was taken care of at his brother Takashi's house while he was restructuring and looking for a job. At home, there is a beautiful sister-in-law, Waka, who is out of proportion to his arrogant brother, and Hiroki wonders why he married Takashi. Waka has never dated a man other than Takashi, and is innocent. It's a waste to have a beautiful body and be full of charm. Thinking so, Yuki teaches Waka the joy of sex instead of his brother.