He was an extremely controversial figure in his own time, and his Buddhism continues to be controversial today. During his lifetime, he sought reform of Buddhism within Japan.
Nichiren believed that the teachings contained in the Lotus Sutra were given by the Buddha Shakyamuni. Not all scholars today believe that the Lotus Sutra was written by Shakyamuni. Many believe it was written by one of his later followers.
One central theme in the Lotus Sutra, which was emphasized by Nichiren and is emphasized in Nichiren Buddhism today, is that enlightenment may be attained in a single lifetime.
He was born in Kominato, which today lies in the Japanese prefecture of Chiba. He began his formal Buddhist study at the Seichoji Temple at eleven, where he eventually became a priest. It was at the Seichoji Temple that he first came to believe in the pre-eminence of the Lotus Sutra. On April 28, 1253, he declared his intention to preach the Lotus Sutra and Namu-myoho-renge-kyo as the true Buddhism. At the same time he changed his name from Rencho to Nichi-ren. "Nichi" means "sun", and "ren" means "Lotus".
He began in the city of Kamakura, where he petitioned rulers to have his form of Buddhism instituted as the state religion and all other sects forbidden. He wrote a religious treatise called the Rissho Ankoku Ron (On Establishing the Correct Teaching for the Peace of the Land), in which he attributed a series of natural disasters including tsunamis and earthquakes as well as foreign invasion (i.e., the Mongols) to the improper practice of the Buddhists.
When Nichiren presented his writing to the rulers, there was a violent backlash against him, especially among the priests of the other Buddhist sects. He was persecuted several times, and exiled at least twice (to the Izu peninsula, and three years on Sado Island).
Nichiren continued to teach his belief in the Lotus Sutra and Namu-myoho-renge-kyo, writing more treatises. Kaimoku Sho (The Opening of the Eyes), Kanjin no Honzon Sho (The Object of Devotion for Observing the Mind) were written while in exile on Sado Island. Also on Sado Island, he composed the Gohonzon, a mandala which he intended as a graphic representation of the essence of the Lotus Sutra--the Mystic Law of cause and effect, which underlies all phenomena in the universe.
He entered a voluntary exile on Mount Minobu in 1274, where he was to spend the rest of his life. He wrote two more major works there, and continued to teach his disciples. The writings were the Senji Sho (Selection of Time) and the Hoon Jo (Recompense of Indebtedness), which was written in memory of his Buddhist teacher, Dozen.
He died in October 1282 at Ikegami, Tokyo, where he had travelled to take medicinal baths for his failing health. He was accompanied by his six disciples - Nissho, Nichiro, Nikko, Niko, Nichiji and Niccho - and other followers. With the exception of Nikko, who dedicated his entire life to helping eternalize his teachings, the other five disciples to a man turned their back on Nichiren's philosophy.