嫁取り×下克上 ～ワガママな3人の姉に下克上セックス!!!～

Kazuki Sawanoi's parents just told him he's adopted.
Not only that, they've issued an ultimatum: he has to marry one of his sisters
after he graduates......!?

Yometori x Gekikujo, an erotic visual novel about a young man picking a wife and the youngest ruling elders!

[From DLsite English]