He is My Master(2005)

Kore ga Watashi no Goshujin-sama

Izumi Sawatari and her younger sister, Mitsuki Sawatari, have run away from home and are in need of employment. The only jobs available are as maids in the mansion of 14-year-old millionaire, Yoshitaka Nakabayashi. What seems like simple work is soon revealed to be far more than the girls bargained for when they find Yoshitaka to be an authoritative employer who demands they call him "Master".

(Source: Sentai Filmworks)