High school student Saito Houjo and his classmate Akane Sakuramori are bitter rivals known throughout their school for their constant bickering and opposing personalities. Saito is a genius who effortlessly gets the top grades, while Akane is a studious and uptight perfectionist who resents that he succeeds without seeming to try. Their contentious relationship is turned upside down when their grandparents, who were also rivals in their youth, reunite as a couple and decide to force their grandchildren into an arranged marriage. Saito’s domineering grandfather, Tenryu Hojō, delivers an ultimatum: marry Akane or lose the family business. Reluctantly, Saito agrees, and to his surprise, Akane also accepts the proposal.

Now living as a newlywed couple in a house prepared by their grandparents, Saito and Akane must navigate the absurd reality of sharing meals, household chores, and even a bed while trying to keep their marriage a secret from their classmates. Their cohabitation is filled with comedic clashes over everyday issues like dishwashing and toilet seats, forcing them to slowly compromise and gain a new perspective on each other's hidden sides. As the story progresses, the initial premise of a forced marriage expands to include the influence of their wealthy families. Saito’s cousin Shisei and his aunt Reiko have their own plans regarding the Hōjō Group inheritance, creating additional complications. The narrative also delves into the characters' pasts, including the traumatic childhood Saito endured with his abusive and parasitic parents, who were eventually expelled from the family by his grandfather. Throughout these events, the distance between Saito and Akane begins to close as they move from enemies to something more, all while questioning what truly motivated Akane to agree to the marriage in the first place.