Since ancient times Hachiman was worshipped by peasants as the god of agriculture and by fishermen who hoped he shall fill their nets with much fish. In the Shinto religion, he became identified by legend as the deified emperor Ojin, son of the Empress Jingo, from the 3rd - 4th century CE. However, after the arrival of Buddhism in Japan, Hachiman became a syncretistic deity, a harmonization of the native Shinto religion with Buddhism. In the Buddhist pantheon in 8th century CE he became associated with the great bodhisattva Daibosatsu.
Hachiman also became to be noted as the guardian of the Minamoto clan of samurai. Minamoto no Yoshiie, upon coming of age at Iwashimuzu Shrine in Kyoto, took the name Hachiman Taro Yoshiie and through his military prowess and virtue as a leader, became regarded and respected as the ideal samurai through the ages. After his descendant Minamoto no Yoritomo became shogun and established the Kamakura shogunate, he rebuilt Tsurugaoka Hachiman Shrine in Kamakura, Japan and started the reverence of Hachiman as the guardian of his clan.
Throughout the Japanese medieval period, the worship of Hachiman spread throughout Japan among not only samurai, but also the peasantry. So much so was his popularity that presently there are more shrines, numbering over 30,000, in Japan dedicated to Hachiman than any other kami. Usa Shrine in Oita prefecture is head shrine of all of these shrines and together with Tsurugaoka Hachiman Shrine and Iwashimuzu Shrine, are noted as the most important of all the shrines dedicated to Hachiman.
The crest of Hachiman is in the design of a tomoe, a round whirlpool or vortex with three heads swirling right or left. Many samurai clans used the tomoe crest as their own, and ironically, by some that traced their ancestry back to the mortal enemy of the Minamoto, the Taira of the emperor Kammu line (Kammu Heishi).