Nikko (April 23, 1626 - April 20, 1698) was a Buddhist monk of Nichiren Sect in the early Edo period. His go (pen name) was Ankokuin. He hailed from Kyoto.
He studied and entered the Buddhist priesthood under Nisshu, a monk of Myokaku-ji Temple (Kyoto City) (Kyoto Prefecture), and thereafter learned the philosophy of Fujufuse school (a school of Nichiren Sect which held philosophy insisting that nothing could be received from or given to people who believe in sutras other than Hokke-kyo Sutra) at Hanko Danrin (seminary) (Hanko-ji Temple in Sosa City, Chiba Prefecture) and Nakamura Danrin (Nichihon-ji Temple in Tako-machi, Chiba Prefecture). In line with the policy to strengthen its control over the Fujufuse school, bakufu (Japanese feudal government headed by a shogun) ordered in 1665 temples of Nichiren Sect to submit a written oath stating to the effect that they admit shuinchi (land granted to temples and shrines by bakufu) is the offering to temples by Kokushu (lord of domain). However, Nichiju of Ikegami Honmon-ji Temple (Tokyo) and other monks who belonged to Fujufuse school at the time refused to submit.
Nikko condemned this policy of bakufu by submitting 'Shusho Gokoku Sho.'
Bakufu further ordered in 1666 to submit a written oath admitting that not only land tax/temple estate but also drinking water and roads were offerings by Kokushu, but Nikko refused again. In the wake of this incident, Nikko was banished to Sadowara in Hyuga Province but he was embraced by the Shimazu clan and conducted propagation there. Nikko wrote his book 'Rokunaikeimo' during that time.
The internal debate in the Fujufuse school, which occurred in 1682 in Okayama, led to the split of Fujufuse school into two schools, namely the Doshi school and the Fudoshi school, and the Fudoshi school to which Nikko belonged became independent as Fujufuse Nichiren Komon Sect.