Nagi Umino is a 16-year-old second-year high school student who learns that he is not the biological child of the family that raised him. On the way to his first meeting with his biological family, he meets Erika Amano, a popular internet celebrity who is trying to escape from an arranged marriage. Later, Nagi and Erika discover that the hospital had accidentally switched the two after their births and their parents are now aiming to put them in an arranged marriage; so they, selfishly, do not have to say goodbye to the children they raised after missing out of their respective childhoods. To facilitate this, they are made to live in a house owned by Erika's family; hoping the two will fall in love before graduation, but will respect their wishes to abandon the idea if nothing comes of it.