Nikkō 日興 (1246–1333, also known as Byaku-ren Ajari 白蓮阿闍梨), one of the Six Senior Disciples (roku-rōsō 六老僧) of 日蓮 Nichiren and the founder of the Fuji-monryū 富士門流 — the Nichiren-school branch which, through successive sectarian splits, became the modern Nichiren Shōshū 日蓮正宗 (and from which Sōka Gakkai in turn split in 1991).
Born in Kai province (modern Yamanashi), Nikkō was a disciple of Nichiren from his early teens and accompanied him through the Sado exile and the Minobu retirement. He was the principal recorder of Nichiren’s late teaching and is credited with the Ongi kuden KR6t0410 (though the Ongi kuden’s precise authorial status is contested in modern scholarship). After Nichiren’s death in Kōan 5 / 1282, Nikkō took over the Minobu headship but split from the Mt. Minobu community in Shōō 2 / 1289 over the shimoyama-zoku doctrinal dispute with Nikō 日向 and other senior disciples and founded the independent Taiseki-ji 大石寺 at the foot of Mt. Fuji in Shōō 3 / 1290 — the future head temple of Nichiren Shōshū. He died at Taiseki-ji in Genkō 3 / 1333, age 88. The DILA authority id is A001251.