After a bitter divorce, Kouhei Kurose and his now ex-wife Yuzuka are hit by a truck moments after signing their papers. Kouhei dies trying to save her, only to wake up as a teenager on the first day of high school, twelve years in the past. He quickly discovers that Yuzuka has also been sent back, retaining all her memories of their failed marriage. Both are filled with regret and hurt, leading them to swear a firm pact to never get involved with each other in this second chance at life, believing that avoidance is the key to happiness.

However, their shared history and deep-seated compatibility make this promise nearly impossible to keep. They find themselves seated next to each other in class and discover they still share the same hobbies. Old marital habits unconsciously surface, creating a series of awkward, humorous, and tender moments. Despite their stubborn denial, the lingering love they still harbor becomes increasingly difficult to ignore. The story follows these two tsundere former spouses as they are forced to confront the reasons their marriage fell apart, learn to communicate honestly, and decide if they can forgive the past to build a new future together.

The narrative primarily unfolds in a modern Japanese high school setting, where both protagonists navigate the contrast between their adult memories and their youthful bodies. The story explores major arcs including the initial shock of their time regression and their determined but failed attempts to separate, the slow process of their walls breaking down as they remember what drew them together, and the final arc where they must address the root causes of their original marital failure. The complete story is a relatively short romantic comedy that concludes with the characters working through their complicated feelings to reach a happy ending.