From Zhiyi's China to Nichiren's Japan

The doctrine did not stay confined to China for long. Saicho, a Japanese monk who studied Tiantai teaching during a journey to China at the very start of the ninth century, brought the tradition home with him and founded the Japanese Tendai school on Mount Hiei near the newly established capital, carrying the interpenetration of the three thousand realms into Japanese Buddhist thought as one of its foundational claims from the outset. Tendai's monastic training center on Mount Hiei went on over the following centuries to educate several of the founders of later, more specialized Japanese Buddhist schools, among them Nichiren, who took the doctrine of the three thousand realms in a single thought and made a concentrated chanting practice built directly on it central to his own new movement in the thirteenth century. The line from Zhiyi's sixth century Chinese formulation through Saicho's ninth century transmission to Japan and on to Nichiren's thirteenth century application is therefore a documented chain spanning three countries and seven centuries, rather than a doctrine that happened to arise independently and by coincidence in each separate setting.

The Tendai school Saicho founded also became, alongside its philosophical inheritance from Zhiyi, one of the two dominant esoteric Buddhist lineages in Japan, incorporating tantric ritual practice his own students brought back from later journeys of their own to China, so that the very school which carried the three thousand realms teaching into Japan also became a center for a form of practice quite different from the philosophical system it is chiefly remembered for today.