To find out more detail see Manual of Nichiren Buddhism

Nichiren selected the Six Senior Disciples: Nisshô Nichirô Nikkô Nikô, Nitchô and Nichiji, on his deathbed at Ikegami on September 8, 1282. He requested them to bury his relics at Minobu, and to take turns in taking care of his tomb and Kuonji Temple in two-month shifts.

Nichiren entered Parinirvâna on the 13th day of next month. His ashes were buried at Minobu on October 26. On January 23, 1283, the one hundredth day memorial service was held for Nichiren at Minobu. Many disciples and lay followers of Nichiren assembled there, but Nikô, and Nitchô were absent. The disciples present discussed their duties at Minobu. The problem was the location of Minobu. Nikkô lived within 60 kilometers from Minobu; and Nichiji, within 80 kilometers. But all the other Senior Disciples lived in farther districts. Kamakura, where Nisshô and Nichirô lived, was 200 kilometers from Minobu; Mama, the residence of Nitchô 280 kilometers; and Mobara, the abode of Nikô, 330 kilometers. In those days travelling was very hard work. It took four days to transport Nichiren's ashes from Ikegami to Minobu. The disciples talked over the problem and decided that twelve more fellow disciples be added to the list of priests on duty, and that the term of shifts be shortened to one month. Thus the schedule of attendance was arranged as follows: January, Nisshô February, Nichirô March, Echizenkô and Awajikô; April, Nitchô May, Nichiji; June, Shimotsukekô and Echigokô; July, Igakô and Chikuzenkô; August, Nichiji and Izumikô; September, Nikkô October, Nikô, November, Nichijitsu and Nichimoku; and December, Jakunichibô and Tambakô. The document of this schedule, which was signed by Nisshô Nichirô Nikkô and Nichiji, is still preserved today. Nikkô signed his name as he was the secretary of the meeting.

The assigned priests attended at Minobu regularly for about one year, but later the priests living in Kamakura were adamant to leave town because they had to defend themselves against the suppression of Nichiren Buddhism which was resumed by the Kamakura Government after the death of Nichiren.

Nagasaki Yoritsuna attempted to eliminate the Daimoku-chanting Buddhists from the city of Kamakura upon the occasion of Nichiren's death. He requested the temples of various sects in Kamakura, including Nichiren temples, to pray for the defence of Japan against another possible Mongolian invasion and also for the peace of the Hôjô family. There were only two Nichiren temples in Kamakura at that time: Nisshô's Hokkeji at Hamado, and Nichirô's Myôhonji at Hikigayatsu.

Nisshô and Nichirô refused to pray for the peace of the Hôjô family because the Hôjôs did not chant the Daimoku but persecuted Nichiren Buddhists. Yoritsuna had anticipated their refusal and intended to make it a pretext for suppressing them. He said that, if they disobeyed the government order, they would be banished from the city, and their temples would be destroyed. For fear that Nichiren Buddhism would be eradicated from the city, Nisshô and Nichirô finally yielded to the order. In 1285 with the petition that the priests of all the sects in Kamakura be assembled to conduct a public debate with Nichiren priests as to what teaching of the Buddha should be considered the most excellent one.

When Nikkô heard of the suppression of Nichiren Buddhism in Kamakura, he sympathized with Nisshô and Nichirô and made up his mind to take care of Nichiren's tomb and Kuonji Temple on their behalf. He wrote to Mimasakabô, one of his friends, on October 18, 1284:

"There is a serious incident (in Kamakura).... Our friends in Kamakura are investigated.... Here we are not troubled.... The tomb at Minobu is trampled by deers. It is too miserable to look at. I do not mean to say that I ignore the duty of the other Senior Disciples ......

Nikkô stayed at Minobu continuously since late 1285. Soon afterwards, Nikô, came to Minobu to help. Nambu Sanenaga, Lord of Minobu, favored Nikô In time, a rift formed between Nikkô and Sanenaga, forcing Nikkô to leave on December 5, 1288.

Nikkô had a disciple called Nichimoku. Nanjô Tokimitsu, Nichimoku's uncle, invited Nikkô to his residence at Taiseki-ga-hara, Ueno, in the Province of Suruga (Shizuoka-ken), and built Taisakiji Temple for Nikkô in 1290. He also helped to build another temple, Hommonji for Nikkô at Omosu, Kitayama, only two kilometers away from Taisekiji Temple, with the cooperation of Ishikawa Yoshitada and others in 1298. Nikkô moved to Kitayama Hommonji in 1298, and spent the rest of his life there.