About Kōya Hijiri

Kōya Hijiri (高野聖) were Japanese monks from Mount Kōya who were sent to preach Buddhism around the country. They were the lowest caste inside the priests' hierarchy of the Mount Kōya temples, and traveled while peddling for a living.
Garbhadhatu (Sanskrit) or Taizo-kai (jp.) - Mandala

Shingon Buddhism – The Japanese root of Esoteric Buddhism

Shingon Buddhism is one of the major schools of Buddhism in Japan and one of the few surviving Vajrayana lineages in East Asia, originally spread from India to China through traveling monks such as and . Known in Chinese as the Tangmi these esoteric teachings would later flourish in Japan under the auspices of a Buddhist monk named (空海), who traveled to Tang China to acquire and request transmission of the esoteric teachings. .