Rokurokubi

Rokurokubi appear across many classical tale collections and Edo-period writings rather than a single unified origin myth. Source tale-collections named in the supplied material that record rokurokubi or nukekubi accounts include Sorori Monogatari, Shokoku Hyaku Monogatari, Kokon Hyaku Monogatari Hyōban, Kasshi Yawa, Churyō Manroku, Hokusō Sadan and others. These narratives variably present the condition as a supernatural yokai manifestation, as an illness found in certain provinces, or as the soul leaving the body during sleep (somnambulism). Some sources (and encyclopedia commentary) also compare related flying-head beings reported in Chinese lore, framing certain variants as foreign or provincial phenomena in Edo-period commentary.

Two principal physical forms are recorded in the sources. In the neck-extension type a person—most often female in tales—appears otherwise human but whose neck can stretch to extreme length; older accounts sometimes describe a ring-like bruise or line around the neck after an incident, and stories mention villagers who concealed such lines with scarves. In the head-detachment type (often called nukekubi) the head separates from the body and floats or flies about freely at night; some tale summaries report the head returning and leaving a visible line or bruise on the neck the following day. Overall, sources emphasize that rokurokubi look nearly human apart from these uncanny differences.

Per the supplied materials, the neck-extension form's primary supernatural attribute is extreme neck elongation; tales generally emphasize the uncanny visual rather than a catalogue of further powers. The head-detachment (nukekubi) form is described in several accounts as able to leave the sleeping body and move through the night; some nukekubi tales attribute harmful acts to the wandering head—examples in the sources include attacking people at night and drinking victims' blood. Sources also treat the phenomenon in some narratives as an illness or as the soul wandering during sleep; these interpretive accounts appear alongside story variants rather than as definitive mechanisms.