The earliest uses of the word akuma are mainly found in Buddhist texts, but it also appears in literary works, especially those written during the Heian period (794–1185 AD).[5] Later, following the introduction of Christianity to Japan, akuma became the customary way of translating the English word Satan.[5]
An akuma is typically depicted as an entity with a fiery head and flaming eyes, and carrying a sword. It is said to be to be a harbinger of misfortune to those who see it.[4]
There have been attestations of people traditionally associating mental illness with the presence of akuma.[6]