Uesugi Ren and his sister Mihato ran away from home because of domestic violence. When they at last reach the city they have a hard time finding work to earn some money. They eventually enter the service of the Kuonji family, making a pledge of absolute loyalty. Thus Ren's days of being a butler to the demanding Kuonji heir begins...

When Saku took in a stray black cat, she never expected that he would become the equivalent of a housekeeping life partner. But Yukichi, a giant cat who towers over Saku, is not your ordinary feline. He takes great pride in his culinary skills, and a good sale at the supermarket always gets his whiskers twitching. Saku may not have her act together yet, but at least she has Yukichi!