This traditional image is constructed centering around the "Ōmagatoki" entry in Toriyama Sekien's *Konjaku Gazu Zoku Hyakki* (Illustrated Hundred Demons from the Present and Past, Continued)^[6], published in the 8th year of An'ei (1779). Ōmagatoki is not a single yōkai, but the temporal condition under which yōkai begin to appear. Therefore, rather than endowing it with a personality and having it attack people, it is treated as the twilight itself—when brightness is lost and the identities of familiar landscapes and people suddenly become uncertain.

Though brief, Sekien's explanation seamlessly links the definition, the uncanny, and a taboo. He first defines the time: "It means twilight. It is the time when the hundred specters arise," and immediately follows with the consequence: "In the world, it is forbidden to let children go outside." The practical warning to bring children home because it is evening and the supernatural explanation that the hundred specters arise form a mutually reinforcing structure. However, this is an explanation of "worldly custom" recorded by Sekien in the late 18th century, and it cannot be definitively said that this exact same prohibition was observed in homes nationwide since ancient times.

In the lower half of the picture, a quiet, unpeopled row of houses and a pagoda resembling a temple stand still, while a large sun is setting on the far left. In the upper half, faces with horns, beast-like faces, and faces that cannot be firmly identified as human or demon peer out one after another from a cloud-like mass. The "hundred specters" (*hyakumi*) do not appear as a roster tallying exactly one hundred entities, but rather as a collective term for numerous uncanny beings whose names and forms remain unfixed. Sekien does not place a single monster in the center; instead, he transforms the entire boundary between the sky and the town into a scene of yōkai manifestation.

The latter half of the text brings up the variant spelling "Hour of Wang Mang" (王莽時). In a theory recorded by Hayashi Razan before Sekien^[3], the day corresponds to the Former Han, the night to the Later Han, and the twilight between them to Wang Mang's Xin dynasty. Sekien retold this older theory, overlaying the historical transition—where Wang Mang usurped the Former Han but his dynasty ended briefly before shifting to the Later Han—onto the boundary between day and night. This does not mean that Wang Mang himself appears as a yōkai; rather, it is an intellectual analogy decoding the sound *ōmagatoki* through the boundary of dynasties in Chinese history. The fact that dictionaries list Ōmagatoki alongside Ōmagatoki (Hour of Great Calamity), Ōmaji (Hour of the Great Demon), and Ōmōji (Hour of Wang Mang)^[1] also indicates that this word has been enveloped in multiple associations: disaster, encounters with demons, and historical intervals.

The terror of Ōmagatoki lies not in the darkness itself, but in the fact that one can still see, yet cannot identify correctly. In complete night, one would prepare a lantern; but at twilight, the sensation of day lingers, and a silhouette thought to be an acquaintance might actually be a stranger. In "Kawataredoki," Yanagita Kunio^[4] surmised that in an era when it was difficult to distinguish a person from the outline of their clothing, people probably could not confirm an individual's identity until they heard footsteps and exchanged greetings. The phrases *taso kare* ("Who goes there?") and *kare wa tare* ("Who is that?") crystallize this uncertainty directly into a question.

In the regional examples Yanagita compiled in *Yōkai Dangi*, voice serves to gauge the boundary between human and non-human. In Saga, a single "Moshi" (Hello) invites suspicion of being a fox; in Okinawa, one does not reply until called three times. The *Game* of Kaga, the river otter of Noto, and the tanuki of Mino and Tosa, even when disguised as humans, cannot correctly pronounce the local dialect, and their true identities are exposed through discrepancies in their responses. [7]However, as Hirota Ryūhei cautions, Yanagita did not clearly indicate the sources for these individual examples, and one cannot conclude that they were all identical Ōmagatoki customs. Here, they are positioned as Yanagita's comparative interpretation linking twilight and the stranger.

There is no fixed value on a modern clock for this hour. Even under the variable hour system of the Edo period^[2], dawn and dusk served as the demarcations between day and night, and their positions shifted with the seasons. The time and duration of twilight differ between summer and winter, north and south, mountains and plains. Charts converting the Hour of the Rooster (kure-mutsu) to exactly 18:00 or 17:00–19:00 today are merely approximations; the essence of Ōmagatoki is not a number on a clock, but the brief transition where daytime visibility and social security begin to unravel.

Therefore, one cannot "defeat" Ōmagatoki. Behaviors such as returning home before sunset, exchanging greetings with companions, and identifying others with a lantern are not magic to erase time, but practical wisdom to reduce uncertainty. When the sun sets and complete night falls, even if the world of the hundred specters continues, Ōmagatoki as the "gap between day and night" comes to an end. The core connecting Sekien's hundred specters, Yanagita's stranger, and the modern fictional use of the hour as a signal for monsters to appear lies in that single point: the unsettling wavering of classification at the boundary where things can be seen but not easily defined.