Sokushinbutsu(即身仏?) refers to a practice of Buddhist monks observing austerity to the point of death and mummification. This process of self-mummification was mainly practiced in Yamagata in Northern Japan between the 11th and 19th century, by members of the Japanese Vajrayana school of Buddhism called Shingon ("True Word"). The practitioners of sokushinbutsu did not view this practice as an act of suicide, but rather as a form of further enlightenment. Those who succeeded were revered, while those who failed were nevertheless respected for the effort.
It is believed that many hundreds of monks tried, but only 24 such mummifications have been discovered to date. There is a common suggestion that Shingon school founder Kukai brought this practice from TangChina as part of secret tantric practices he learned, and that were later lost in China.
There is the existence of at least one "self-mummified" 550 years old corpse of a Buddhist monk named Sangha Tenzin in India, visible in a temple in Gue village, Spiti, Himachal Pradesh. This mummy was found in 1975 when the old stupa preserving it collapsed. Virtually all stupas contains relics, so it could be possible that several other mummies hide inside of ancient stupas all over the Himalaya and Tibet. The mummy has been carbon dated between 550 and 600 years ago. The monk was likely a dzogpa-chenpo practitioner. A scientific team believes the mummification process was possible because his tantric practice involved total abstinence from food, eliminating intestinal bacteria and fats: "Mair draws parallels between Sangha Tenzin and a Buddhist monks of Yamagata in northern Japan...". The preservation of the mummy for at least 5 centuries has been possible also thanks to the aridity of the area, protected from the Monsoon by the Himalayan range. Although the tradition of "self-mummification" could have spread into the Western Himalaya from China, it's not possible to exclude that the origin of Sokushimbutsu lies in tantric practices af ancient India.
Today, the practice is not advocated or practiced by any Buddhist sect, and is banned in Japan.
The practice was satirized in the story "The Destiny That Spanned Two Lifetimes" by Ueda Akinari, in which such a monk was found centuries later and resuscitated. The story appears in the collection Harusame Monogatari.
In the Megami Tensei games, a practitioner of Sokushinbutsu known as Daisoujou makes numerous appearances.
In the InuYasha series, a monk by the name of Saint Hakushin went through the process of Sokushinbutsu in times of famine and war in order to be able to protect his people forever as a living buddha. During the process he realizes the people outside are waiting for him to die and begins to resent them, allowing his undead mummified body to be convinced to help the main villain with his vast sacred powers.
In Osamu Tezuka's Phoenix: Karma, Saruta's mentor commits suicide in this manner because he has been driven to despair by the government's misuse of Buddhism for political gain.
In the Sandman Slim novel The Getaway God the main character works with a Sokushinbutsu who remained alive and meditating for 400 years before resuming activity.
Hori, Ichiro (1962). "Self-Mummified Buddhas in Japan. An Aspect of the Shugen-Dô ("Mountain Asceticism") Sect". History of Religions1 (2): 222–242. doi:10.1086/462445. ISSN0018-2710. JSTOR1062053.|access-date= requires |url= (help)
Hijikata, M. (1996). Nihon no Miira Butsu wo Tazunete. [Visiting Japanese Buddhist Mummies]. Tokyo: Shinbunsha.
Jeremiah, K. (2009). Corpses: Tales from the crypt. Kansai Time Out, 387, 8-10.