Miki Koishikawa, a high school student, experiences a dramatic shift in her life when her parents announce their divorce and reveal they have swapped partners with another couple, the Matsuuras. The two families decide to live together under one roof, blending their lives in an unconventional arrangement. Miki struggles to adjust to this new dynamic, particularly when she meets Yuu Matsuura, the son of the other couple. Yuu is charming, confident, and seemingly unfazed by the situation, which contrasts sharply with Miki’s initial discomfort and resistance.

As Miki and Yuu navigate their shared living space, their relationship evolves from tension to a complex mix of friendship and romantic feelings. The series explores their growing bond alongside the challenges posed by their intertwined families. Miki’s ex-boyfriend, Ginta Suou, complicates matters further as he re-enters her life, creating a love triangle that tests her emotions and loyalties. Meanwhile, Yuu’s past relationships and his own unresolved feelings add layers of complexity to their interactions.

The narrative delves into themes of love, family, and identity, as the characters grapple with their changing circumstances. Miki’s journey is central, as she matures and learns to navigate her feelings for Yuu while reconciling with her parents’ decisions. Supporting characters, such as Miki’s best friend Arimi Suzuki and Yuu’s former flame Meiko Akizuki, contribute to the story’s emotional depth, each bringing their own struggles and perspectives.

Throughout the series, misunderstandings, miscommunications, and external pressures create obstacles for the characters, but their relationships gradually deepen. The story balances moments of lighthearted humor with poignant drama, capturing the ups and downs of adolescence and the complexities of human connections. By the end, the characters’ growth and the resolution of their conflicts provide a satisfying conclusion to the series, highlighting the enduring impact of love and family.