Kimi ga Aruji de Shitsuji ga Ore de (2008)

Original title: 君が主で執事が俺で

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...