吉冈春（池胁千鹤 配音）是一个普普通通同时又有些迷糊的女高中生，某天放学的路上，她偶然救下了一只险些丧生车轮之下的小猫，谁曾想小猫竟然直立起来以人类的方式对女孩表示感谢。小春更想不到的是，她不经意的善举改变了自己的命运。原来小猫是猫王国的王子，为了报答小春的恩情，猫王国举国上下展开了令人啼笑皆非的报恩行动，只不过它们视为“上品”的老鼠令小春哭笑不得。不久后，小春接受王国的邀请前去做客，期间竟稀里糊涂答应成为王子的妃子。女孩眼看就彻底变成了一只猫，神秘的男爵（袴田吉彦 配音）成为她的救命稻草…… 　　本片亦被视为《侧耳倾听》的番外篇。A young girl rescues a mysterious cat from traffic and soon finds herself the unwelcome recipient of gifts and favors from the King of the Cats, who also wants her to marry his son, Prince Lune. With the assistance of a fat, grouchy real cat and a an elegant cat statuette come to life (both characters featured in Studio Ghibli's earlier anime "Whisper of the Heart"), the girl visits the Cat Kingdom and narrowly escapes again.