Temple tradition holds that Hatakeyama Shigetada founded Sankaiji at Yoritomo's command during the Bunji era (1185–1190). The establishment of a Shingon center at this strategic point in Tachibana County, Musashi Province, during the dawn of the Kamakura shogunate reflects the religious network built to support eastern rule. The principal image, a Kamakura-era Maitreya, still carries the prayers of Yoritomo's age.

A Shingon temple said to have been founded by Hatakeyama Shigetada at Yoritomo's command. Shigetada, together with Hojo Tokimasa and Yoshitoki, was a pillar of the early Kamakura shogunate — a tragic warrior later killed in 1205 through the slander of Tokimasa and Maki no Kata. As a temple tied to Shigetada, Sankaiji preserves the memory of Masako's era as principal consort of the Kamakura lord, when she watched over both her husband and Shigetada.