[Nitta Jun] Secret deals (Doutei Chinkonkan) [NyaaTranslate]

A bold sister strikes a secret bargain after getting an eyeful of her brother and his friend, comparing the thick one and the long curved one before deciding her peeping virgin brother deserves the real thing. Recruiting Kaori, a shy schoolgirl who obediently strips bare and answers to senpai, she lays the nervous girl out on the bed and takes charge of the whole defloration — ordering fondling, gripping his balls so he doesn't finish too fast, and demanding he stroke his hips harder. What starts as teasing curiosity between siblings turns into a hands-on first-time lesson that leaves everyone thoroughly educated.