Kakkou no Iinazuke

A high school student named Nagi Umino discovers he was switched at birth and is set to meet his biological parents. While en route to the dinner, he encounters Erika Amano, a bold girl who wants to pretend to be his girlfriend to avoid marriage. At the dinner, Nagi learns his birth parents have arranged for him to marry the girl they raised, who is revealed to be Erika.