Kaiki

Kaiki is a Japanese term written as 怪異, commonly translated as “mysterious phenomenon” or “strange affair.” The word combines 怪 (strange, mysterious) and 異 (different, unusual). In Japanese folklore and literary tradition, kaiki refers to occurrences, entities, or phenomena that defy ordinary explanation, ranging from hauntings and omens to ambiguous creatures. It is related to, but not identical with, yokai, a more specific class of supernatural beings.

In classical and modern storytelling, kaiki is used to evoke mystery and the unknown. Narratives may describe a kaiki encounter as a turning point or a test for characters, sometimes with a moral or cautionary dimension. In contemporary media, kaiki also appears as a proper noun: for example, Kaiki Deishu is a recurring character in the Monogatari light novels and anime, presented as an occult expert and con artist who trades in information and manipulation.

Beyond literature, the term is occasionally found in academic or folkloric discussions of Japanese supernatural belief, where kaiki is part of the broader vocabulary for describing strange occurrences that inspire curiosity, fear, or wonder. It is not a fixed category like youkai but a general label for phenomena that seem to exceed everyday explanation.