Kumagai Naozane was born in Kumagai village, in the Osato District of Musashi Province, Japan. Original personal name: Jiro. He was the son of Naosada Kumagai. He lost his father at a young age, and was raised by his maternal uncle, Hisaka Naomitsu.
Kumagai Naozane is particularly known for his exploits during the Genpei War, specifically for killing the young warrior Taira no Atsumori at the battle of Ichi-no-tani in 1184.
Later in life, Kumagai Naozane is also known in Japanese Buddhism as a devout follower of Honen and the new Pure Land movement, as well as his renunciation of the samurai life.
Kumagai Naozane fled to Kyoto and became a disciple of Genku under the Buddhist name of Rensei. Afterward went to Kamakura and was consulted by Yoritomo on military strategies. Yoritomo beseeched him to become a warrior again but Naozane refused the proposal.
Kumagai remained remorseful over the people he killed in his career as a soldier, and grew discontented with following Minamoto no Yoritomo, so he visited the Pure Land Buddhist monk, Hōnen and explained that he was concerned with the afterlife. Hōnen told him that he need only recite the name of Amida Buddha, the nembutsu, and that regardless of his former life he would be reborn in the Pure Land.
From there, Kumagai became a close follower of Hōnen and Jōdo-shū Buddhism, and took the ordained named Rensei. Rensei later made a written vow before a statue of Amida Buddha, stating that he would strive to reach the highest rebirth in the Pure Land As a close disciple of Hōnen, Rensei became a popular instructor on Pure Land Buddhism and helped spread the new doctrine to others who also became Hōnen's disciples. In the summer of 1206, Rensei/Kumagai died one morning while repeating the nenbutsu over and over in front of a hung image of Amida Buddha and his attendant Bodhisattvas.
