In his conquest of Japan, the great warlord Toyotomi Hideyoshi (1536 -1598) wanted the major temples of the Kii area to submit to his authority. In 1585, when Negoro-dera refused, it was burned to the ground.

Mt. Kōya was subsequently placed under siege by Hideyoshi’s forces with the demand that the monastery give up its weapons, some of its land holdings as well as its right to provide sanctuary.

The priest Ōgo was sent to Hideyoshi to negotiate.

Ōgo, who had been born into a military family in Omi, took holy orders at Mt. Kōya in 1573 at the age of 38. As part of his religious austerities, he subsisted only on nuts and berries, and is therefore also known as Mokujiki Shōnin, “The Tree Eating Saint.”

Sharing similar backgrounds, Hideyoshi and Ōgo and soon developed a strong mutual trust, and an agreement was reached: Mt. Kōya would give up a major share of its wealth, but in return Hideyoshi would become a generous patron, donating over the course of several years the funds for the reconstruction of the Kondō and the establishment of a temple for his mother. (This became Seiganji, which was later merged with another temple to create the present-day Kongōbuji Temple.)

Ōgo eventually became Abbot of the monastery at Mt. Kōya and, in later years, he would convince Ishida Mitsunari to contribute funds for a large sutra repository. This building still stands near the Kōbō-daishi’s mausoleum and is one of three places at Oku-no-in recognized as World Heritage sites. Ogo’s association with the losing side in the ultimate battle for supremacy during the Warring States period forced him to resign his position as abbot and to leave the monastery.

After his death in exile, his remains returned to Mt. Kōya and now rest in a small mausoleum near the Tamagawa River. The small wooden building is said to contain a stone monument in the hōkyōin-to style.