Nichison, one of Nichiren's direct disciples, devoted himself to spreading Nichiren Buddhism. He particularly contributed to missionary work in the Kanto and Tokai regions and also had exchanges with Ji-shu (the Time school) founded by the wandering saint Ippen. As one of the Six Elder Monks designated by Nichiren as successors, he played an important role in transmitting the master's teachings to the provinces. He maintained faith through the turmoil of the Northern and Southern Courts period and contributed to building the organizational foundations of Nichiren Buddhism.