Ninna-ji is known as a monzeki temple. This denotes that the temple has a history of imperial family members joining the temple to become Buddhist priests. The word monzeki was also used to refer to the former emperor or prince who had become the head priest of the temple.
The first emperor to abdicate the throne and join a Buddhist temple was Ninna-ji’s first monzeki, Emperor Uda. This started a long chain of head priests who were part of the imperial family. After the Meiji Restoration, the practice of sending imperial family members to serve at temples was stopped, but out of tradition head priests at Ninna-ji continue to be referred to as “monzeki.”