Teenager Haru is bored and frustrated by her life as a schoolgirl in modern-day Tokyo. When she saves a cat from certain death on a busy road, she has no idea of the extraordinary chain of events she is setting in motion. For the lucky animal is none other than Prince Lune, heir to the throne of the strange and enchanted Kingdom of Cats. Haru journeys to this remarkable land, where she is showered with gifts and overwhelmed by the gratitude of its feline citizens. When she learns that the Cat King plans to marry her off to his son, Haru plots her escape, with the help of Baron Humbert von Gikkingen and his animal henchmen. But as the Kingdom works its insidious magic, Haru's resolve weakens. The allure of her new situation becomes harder and harder to resist, and she grows ever more cat-like. Can Haru withstand the dangerous charms of the Kingdom and retain her identity? Can she return to her own world? Or will she succumb?