A brother-in-law who decided to live with his younger brother and his wife for a short time due to work.Yukino, who lives harmoniously with his younger brother, is also dissatisfied and lonely with his husband who does not encourage child-making.The brother-in-law, who sensed such a suicide, approached Yukino instead of the unscrupulous younger brother.Yukino refused to be unfaithful, but her repeated brother-in-law's cunnilingus made her feel uncontrollable and had a relationship.Yukino who was fascinated by gentle and rich caresses seduces her brother-in-law and drowns in an unfaithful relationship.