Nounai Kanojo - Zettai ★ Imouto Shijou Shugi!!

Shinichi has many sisters who treat him coldly. But almost all of his sisters leave the house to work or study, and his life becomes peaceful. He sometimes gets confused by Minato's deeds, who is the youngest sister, but he somehow enjoys his life. But a turning point comes suddenly...
During spring holiday, his father adopts a girl, Amane. He welcomes her since she is quiet. But Madoka, his younger sister, comes back to his house, and controls him. He can't stand it anymore, and decides to get back the power!