Nichikō was a monk in the Nichiren sect of Zen Buddhism during the Azuchi-Momoyama period. He lived from Tenbun 1 (1532) to 8/27 of Keichō 3 (1598). Nichikō was a prominent scholar and high-ranking priest with a large following among his disciples.
His pseudonym was Ryūunin or Busshinin. His father, Abura Date Jōgen, was a wealthy merchant in Sakai engaged in the sale of medicine.
Nichikō entered the Chōgen Temple in Sakai and studied at the Onjō (Mitsui) Temple and the Enryaku Temple on Mount Hiei. Impressed by Nichikō’s broad erudition, his master on Mount Hiei named Sonkei presented Nichikō with a sacred purple kasaya (a stole) from a monk named Saichō who founded the Tendai sect of Zen Buddhism in the eighth century during the early Heian period.
In 1555, Nichikō became the third-generation head of the Chōmyō Temple in Kyōto. In 1558, he revitalized the Chōgen Temple and acquired the faith of the Miyoshi family in Kawachi Province. Initially, he engaged in active proselytism. In 1579, after a religious debate against adherents of the Jōdo (Pure Land) sect of Buddhism organized by Oda Nobunaga (an event known as the Azuchi Religious Debate), he changed to a peaceful manner of conversion by implicitly recognizing other’s beliefs.
Later, Nichikō was invited by Tokugawa Ieyasu to become the twelfth head of the Hokekyō Temple in Chiba-Ichikawa affiliated with the Nichiren sect. Meanwhile, the Miyoshi clan donated land and the Myōkoku Temple built on Mount Kōfu in Sakai by his father, Jōgen, was founded.
In the fifth month of 1579, with the aim of suppressing members of the Nichiren sect, Oda Nobunaga ordered Nichikō to attend the Azuchi Religious Debate. According to Nichikō’s diary, he was subject to religious persecution on 5/27, and from 5/29 until 6/12, was ordered confined to the Shōkaku Temple at Azuchi. On 6/12, he was pardoned and, after traveling through Sakamoto and Kyōto, returned to Sakai on 6/22. While in Azuchi, he was remonstrated by Nobunaga to either change his religious tenets or throw-away his life and punched, leaving him in a bad condition. He was then forced to write a confession and mark a mandala in a seal of blood.