Shin gon: True Word
An esoteric school of Japanese Buddhism. Its name is a translation of the Sanskrit term mantrayana ("vehicle of the sacred words"). The school was founded in 808 by Kukai (774-835), also known by his Chinese name of Kobo Daishi. Kukai had been to China where he spent 2.5 years studying the Chinese translations of the newly arrived esoteric teachings of Indian Buddhism and Tantra. He studied and practiced with masters of the Mi-tsung (Chin., School of Secrets), a school that was never to gain a strong foothold in China. Through Kukai, however, these teachings reached Japan where today, Shingon is one of the three largest Buddhist schools.
Shingon teachings are divided into Ken-kyo (Jap., exoteric teachings) and Mitsou-kyo (Jap., esoteric teachings), and it was mainly the latter that had interested Kukai; the esoteric rituals, practices and teachings are clearly predominant in early Shingon.
Although Shingon is widely regarded as a form of Mahayana Buddhism, a closer look reveals that it is really a mixture of various influences:
The eclectic nature of Shingon, and the existence of exoteric and esoteric teachings, led to many branches, sub-divisions or sects. Some of these used sexual symbolism only, for example in the goma fire ritual - while others also used the sexual force in practice. About three centuries after Kukai’s death, the specifically sexual teachings that were part of esoteric Shingon were slowly being diluted and more or less suppressed by and the then ruling leadership.
Nin-kan (1057-1123) and others who did not agree with this development, branched off (in 1114) and continued those practices in the Tachikawa-ryu.