In the Twelve City, a modern Japanese town where humans and yokai coexist, twelve ruling families each bear the name and power of a Chinese zodiac animal. This system originates from an ancient divine selection, where the rat arrived first by riding on the ox's back, while the cat was tricked by the rat and missed its chance entirely. Consumed by this betrayal, the excluded cat transformed into a hateful yokai, cursing its descendants with an existence sustained by vengeance against the rat clan.

Kyouichi Nekuni is the formal head of the Rat Family, but he is considered a failure because he inherited no supernatural powers. One day, a cat yokai appears before him with clear intent to kill. This is Natsuho Nekogasaki, a young woman from the Cat Clan, whose very being is forged from the grudge against Kyouichi's family. Yet despite this mission, Natsuho is painfully shy and anxious around other people. When she finally has the chance to kill Kyouichi, she hesitates and instead begins observing him. Through this forced proximity, Natsuho discovers that Kyouichi is a kind but apathetic young man who resents his own family's ruthlessness and his powerless position within it. She grows attached to him, directly contradicting the curse that demands her hatred. If she stops hating Kyouichi entirely, the hatred sustaining her existence may cause her to disappear.

Kyouichi and Natsuho are soon joined by Ayaka Ushigura, the head of the Ox Clan, a powerful and tomboyish young woman who has been Kyouichi's childhood friend and self-appointed bodyguard since birth. Ayaka harbors romantic feelings for Kyouichi, creating a complicated romantic triangle as she also forms a close friendship with Natsuho that becomes crucial to Natsuho's emotional growth. Together, the three confront not only Natsuho's internal battle against the voices of hatred in her head but also an external villain who initially manipulated Natsuho and continues pulling strings behind the scenes, orchestrating conflicts among the twelve families.

As the series progresses, Kyouichi evolves from a passive victim of his family's expectations to someone who actively works to initiate change from within. Natsuho gradually outgrows her inherited hatred, making friends and learning to trust despite her crippling shyness. The narrative moves between serious battles against the mastermind villain, slice-of-life comedy, and the evolving romantic tensions among the three leads. Later arcs introduce the revelation that the current head of the Cat Clan is actually Fuyuho Nekogazaki, not Natsuho, deepening the mysteries of Natsuho's past and her family's true nature. The story ultimately concludes with Kyouichi and Natsuho finding peace and resolution, having grown through each other's support while the curse of hatred is finally addressed.