Meido deka (2009)

18-year-old Aoi Wakatsuki works as a maid in a huge Kyoto mansion for the wealthy Sengoku family. What others are not aware of is that Aoi is actually working undercover to investigate the death of a former Sengoku maid. Her death was initially ruled a suicide with a suicide note left behind confessing she broke a priceless vase. Inspector Toshiaki Kaido isn't convinced the maid committed suicide, especially with the Sengoku family refusing to cooperate. Inspector Kaido then employs his own maid Aoi Wakatsuki to work for the Sengoku family and uncover the truth.