This role-play is performed by adults. ``I never expected that I, who was an ordinary housewife, would grow up to have this kind of relationship with my younger brother...'' Aya Kurahashi (Ai Kano), an older sister in her late 30s with two children, is contracted to do housework for her younger brother Takumi, a single aristocrat in his 30s, in order to make ends meet. However, before he knew it, Takumi had discovered his fetish for mature women and had a secret desire for Aya... Takumi, who had gotten into a relationship with her after getting drunk, continued to pursue her and proposed a relationship with her. Even though she says it's for the sake of the family's finances, Aya's body drowns in guilty pleasure as she experiences the pleasure of an affair for the first time...