The Treasure of The King and The Cat
Ou to Neko no Hihou
One day, a large number of people suddenly disappeared in the royal capital. When young King Castio goes out to investigate this occurrence, he comes across the culprit... but the criminal puts a spell on him! To help him out, the king calls the wizard O'Feuille to his castle, along with Prince Volks and his loyal retainer Nios. Together, they're determined to solve this strange, fluffy mystery full of cats, swords, and magic!
(Source: Tokyopop)