Sozan' is Kuon-ji Temple located on Mt. Minobu (which is considered to be the sacred mountain where Nichiren as a god lives) where Nichiren's remains were buried by his will, and Kanju (the head priest) of Sozan is called 'Hoshu.'
祖山は日蓮の遺言に従い遺骨が埋葬された祖廟がある身延山久遠寺（日蓮棲神の霊山とされる）で、貫首を法主と称する。