I forgot the name of the doujinshi but it was these 3 sisters. The oldest one has hairy pussy and big boobs, middle one has shaved pussy and medium sized boobs and the youngest one has small boobs too. They were at a homestay looking place to live and theres a guy that takes cares of them. One night the middle sister has trouble with the computer so the guy fixed it and porn showed up on the screen, then the girl insisted on having sex but the youngest one saw everything. Then the oldest one and the middle one had a school trip leaving the guy and the youngest one alone. The little sister threatened to blackmail the guy unless he has sex with her so he did. Then the last chapter is the guy having sex with the oldest sister