Haru, a quiet and unassuming high school student, has her life turned upside down one day when she rescues a cat from being run over by a truck. To her astonishment, the cat she saved reveals itself to be Lune, Prince of the Cat Kingdom. As a token of gratitude, the Cat King showers Haru with gifts and honorably invites her to marry Prince Lune. Confused and overwhelmed, Haru begins to notice strange transformations in her life and is soon whisked away to the mystical Cat Kingdom against her will.

Desperate for help, Haru seeks guidance from the enigmatic Baron, a dapper feline statue that comes to life, and his friends Muta, a fat white cat, and Toto, a crow. Together, they embark on an adventurous journey to navigate the whimsical and often perilous world of the Cat Kingdom. As Haru becomes more entangled in the bizarre customs and politics of the feline realm, she must rely on her newfound allies to find a way back to her own world before she is permanently transformed into a cat.