In 1476, Ota Dokan founded Seishoji by inviting the Zen master Unko Shuntoku to a site at Musashino Kaizuka. Under Dokan's patronage the temple grew into a major Soto Zen center and laid the foundation for what became one of the three administrative Soto Zen temples governing religious affairs throughout Edo. More than five centuries after its founding, the temple still stands on the slopes of Atago Hill.