Isahaya Ichi is fed up with men, a woman navigating a world where she's underestimated at work because of her gender and sexually harassed. But when her former classmate, Masaki, unexpectedly shows up, everything changes. He claims to be the other half of her "destined pair" from a junior high school event called "Gene Bride," where genetic information matched students into couples for a day. While Ichi barely remembers the event, Masaki's sudden reappearance sparks a journey of rediscovery and buried secrets.