Kono Naka ni Hitori, Imouto ga Iru!

Shougo Mikadono faces an unusual challenge upon inheriting his father's company: he must first find a wife at school. The catch? One of the potential brides is his long-lost sister, separated from him in childhood and now hidden among the student body. This bizarre stipulation, coupled with his father's eccentric will, plunges Shougo into a high-stakes romantic mystery. As Shougo navigates the complexities of school life and the persistent advances of several eager young women, he grapples with the unsettling possibility that any of them could be his sibling. He'll need to uncover the truth of his past and the identity of his sister before he can secure his inheritance and, perhaps, find true love — or something even more complicated.

✦ AI-drafted summary