Tsukioka Yoshitoshi, The Fever, August 1883. Triptych, 28.25" by 13.75".
Pictured: Kiyomori dying from his fever with King Enma as well as the ghosts of Kiyomori's victims watching over him.
Disclaimer: This image is of the free public domain. Retrieved from https://commons.wikimedia.org/wiki/File:Yoshitoshi_The_Fever.jpg through SnappyGoat.com.
King Enma is mentioned twice in Book 6. In episode 7, Lady Nii has a terrifying dream that involved a fiery carriage drawn by hell fiends who have declared that they’ve come by order of King Enma to bring Kiyomori to Muken, the hell of unbroken agony. Then again in episode 9, scholar monk of Mount Hiei Jishinbo Son’e has an elaborate dream in which he was brought a letter from King Enma that commanded him to appear for the gathering of 100,000 devotees who were to chant the Lotus Sutra. When Son’e came in the next dream, King Enma gave him insight that lead him to believe that Kiyomori was the reincarnate of the great Buddhist master Jie.
King Enma, even in the text, is described at the guardian of hell unbroken agony, or Muken. Muken is short for muken jigoku (無間地獄) and literally means “uninterrupted hell” or “Hell of No Interval” (Hirasawa, 3). For those only somewhat familiar with Buddhism, it may seem counterintuitive for a culture so engaged with Buddhism at this time in medieval Japan (12th century) to believe in a hell, given that the most general understanding of Buddhism is the belief in cycle of rebirth only to be broken once one reaches enlightenment. However, due to a combination of indigenous beliefs as well as the fact that most, if not all, sects of Buddhism do describe various hells, depictions of hell started appearing in Japanese literature and art as early as the Nara and Heian periods, known as the classical period.
Indeed, the concept of hells as places of punishment originated with Indian Buddhism and evolved with the evolution of Buddhism as it moved from India to China to Korea and finally to Japan. Hirasawa notes that “Chinese translations of Indian sutras and commentaries that circulated widely in Japan, hell functioned as part of an immense cosmology” (2). In these commentaries, there are eight great hells, with Muken being the deepest and worst. As the worst hell, Muken is supposedly reserved for those who have committed the utmost evil of sins such as killing their parents or injuring a Buddha. This makes the gravity of Lady Nii’s dream in which he was summoned to Muken by King Enma much more potent, especially considering the role of Kiyomori in the Hogen conflict, in which he was made to kill his uncle. This also alludes to the fact that Kiyomori may or may not have committed other grave sins in his lifetime.
As for King Enma himself, it appears that his character was developed in early Buddhism in India and also evolved with Buddhism as it moved to East Asia. In Japanese paintings, he was often depicted in Indian clothing. According to Hirasawa, “described in the Vedas as the ancestor of humanity, the first to die, and governor of a paradisical land of the dead” (11). Even in Japan, he was first seen as heavenly figured then during the Heian period, he developed into a being that descended to hell to eventually become the king that makes judgement on the souls of wrongdoers.
Source: Hirasawa, Caroline. “The Inflatable, Collapsible Kingdom of Retribution: A Primer on Japanese Hell Imagery and Imagination.” Monumenta Nipponica, vol. 63, no. 1, 2008, pp. 1–50. JSTOR, JSTOR, www.jstor.org/stable/20535182.