A perverted younger brother comes to his married older sister's house for the first time in a long time. When his sister was still single, he repeatedly had sex with her and treated her as a sex slave. The younger brother, who doesn't have the money to pay for sex, plans to rape his sister while his brother-in-law is sleeping, but when his brother-in-law happens to be away on a business trip, he plays with his sister's voluptuous body without hesitation and cums inside her as many times as he wants, instead of his brother-in-law.