Department of the Imperial Household
Historical government body responsible for matters related to the Imperial Family; replaced by the 宮内庁 (Imperial Household Agency) after WWII.
See also: 宮内庁
Before the war, the Department of the Imperial Household handled the affairs of the Imperial Family.
From 宮内 (inside the palace) + 省 (ministry/department). The name reflects its role as the ministry overseeing palace affairs.