Sometimes a bear, sometimes a mouse—Princess Fluorite possesses a supernatural power that causes her to transform into animals regardless of the place. Because of this troublesome power, her fiancé ran away, and she was on the verge of becoming a "leftover bride." Then, a marriage proposal arrived with the Crown Prince Jade (21 years old), who is exactly her type. Fluorite was overjoyed with this perfect match, but the person who appeared was a lovely, beautiful boy of about seven years old!? It seems that Jade is under a curse that turns him into a child only during the day, and the key to breaking the curse apparently lies with Fluorite...?