Nagisa Umino, a high-achieving student, and Nagi Umino, a carefree and somewhat lazy teenager, discover they were accidentally switched at birth. Their lives take an unexpected turn when their biological parents arrange for them to live together to foster a relationship, with the ultimate goal of marriage. This arrangement is intended to resolve the complications arising from their switched upbringing and to unite their families. Despite their initial reluctance, Nagisa and Nagi agree to the plan, setting the stage for a series of comedic and dramatic interactions.

Nagi, who was raised in a wealthy household, struggles to adapt to his new life with his biological parents, who are more modest and traditional. Nagisa, on the other hand, finds herself navigating the unfamiliar dynamics of Nagi’s affluent family. The series explores their evolving relationship as they grapple with their feelings for each other and the expectations placed upon them. Alongside this central dynamic, the story introduces several other characters who add complexity to the narrative. Erika Amano, a cheerful and outgoing girl, becomes a love interest for Nagi, creating a love triangle that drives much of the romantic tension. Hiro Segawa, a childhood friend of Nagi, also harbors feelings for him, further complicating the relationships.

As the story progresses, the characters confront their insecurities, ambitions, and emotions, often leading to humorous misunderstandings and heartfelt moments. The narrative delves into themes of identity, family, and the challenges of adolescence, blending lighthearted comedy with moments of introspection. The series balances its romantic elements with a focus on personal growth, as Nagi and Nagisa learn to navigate their intertwined lives while pursuing their individual goals. The interplay between the characters and their evolving relationships forms the core of the story, offering a mix of humor, drama, and romance.