Nakaimo: My Little Sister Is Among Them! (2012)

Shougo Mikadono finds himself in a bizarre predicament after his father’s will stipulates that he must attend a new school and marry a girl to inherit a massive fortune. While initially appearing straightforward, the quest becomes a complicated mess when Shougo realizes that one of the girls he’s drawn to is actually his long-lost sister, and he has no clue which one it is. As he navigates the challenges of romance and family ties, Shougo must tread carefully to avoid crossing ethical lines and uncover the truth about his sister’s identity without igniting chaos.