Having a lover who doesn't know how to keep it, often going out alone and always being indifferent, even though her lewd sister Shinoda and her boyfriend do shady things are things that she regrets later. Since accidentally seeing the sex scene of her sister and her lover, in her sister-in-law's mind, the extreme desire of an unmarried woman has appeared. Then when the younger brother was away, she always deliberately did erotic and provocative actions in front of the other guy so that his cock could not control himself and was easily fascinated by her too slim body and extremely attractive breasts. Since that time, they have always secretly carried out clumsy love affairs behind her sister's back everywhere in the house, when she is away or sleeping, even when she finds out, they both ignore it, do not care at all, but deliberately continue to rain in happiness without thinking about the feelings of their sister this misfortune.