What is "seizan"

is the name of the branch of Jōdo-shū Buddhism that was founded by Hōnen's disciple, Shōkū. Shōkū often went by the name Seizan as well, however the name derives from the western mountains of Kyoto where Shōkū often dwelt. The main temple of this branch of Buddhism is at the temple of Eikandō in the city of Kyoto. The temple formerly served as a Shingon Buddhist temple, but when Jōhen headed the temple, he took an interest in Jōdo Buddhism (originally in order to criticize it), designated Hōnen as the 11th chief priest. Later, Hōnen's disciple became the head priest of Eikan-dō, and established the Seizan branch, fully converting the temple into a Jōdo one.