With the exception of Nagi, a solemn and shy young man who only cares about his studies, the members of the Umino family are all quite similar: they are all extremely active and enthusiastic. Like his younger sister Sachi, who is a reflection of her outgoing parents, he is the exact antithesis of that person. Therefore, it shouldn't be shocking that Nagi was switched with another child at birth. Erika Amano, a young social media sensation, is encountered by Nagi as he travels to see his real parents. He finds out about Erika's forced marriage while spending the day with her. Later on that day, Nagi finds out that Erika's fiancé is actually him, thus they can be recognised as members of each other's families. Nagi's biological father sets up for the engaged couple to begin living together in an effort to strengthen their love! No matter what their parents do, Nagi won't agree to marry Erika. That's because he already has Hiro Segawa in his sights, who is both attractive and intelligent.