According to the description in Volume 12 of the *Taiheiki*^[1], the original source for the Itsumade, in the autumn of the first year of Kenmu (1334), amidst a nationwide epidemic causing numerous deaths, a monster bird appeared above the Shishinden in Kyoto night after night. The bird cried out "Itsumade, itsumade," striking great terror into the hearts of the courtiers. The nobles, following the precedent of Minamoto no Yorimasa shooting down the *Nue*, sought out a master archer, and Oki no Jirōzaemon Hiroari was chosen for the task. Nocking a *karimata* (fork-headed) whistling arrow, Hiroari splendidly shot down the monster bird from the dark sky, and it is said that Emperor Go-Daigo granted him the surname "Mayumi" (True Bow) and a manor in Inaba Province. The form of the fallen monster bird was such that its head was like a human's, the tip of its beak curved and lined with saw-like teeth, its body resembled a snake, and both of its legs possessed sharp, sword-like spurs.

Over four hundred years later, in the Edo period, Toriyama Sekien visually reconstructed this monster bird in the "Rain" volume of his *Konjaku Gazu Zoku Hyakki*^[2] (1779). In Sekien's illustration, in addition to the snake-like body described in the *Taiheiki*, the bird is depicted flying through a night sky adrift with dark clouds while spewing ominous flames from its mouth. The accompanying text simply states, "The matter of Hiroari shooting the monster bird that cried 'Itsumade, itsumade' is detailed in the Taiheiki," intentionally leaving the detailed explanation to the classic literature. However, by giving it the name "Itsumade" based on its cry, he elevated the nameless anomaly into a definitive character. This is one of Sekien's typical naming techniques in his yokai illustrations.

From the Shōwa period onward, in yokai-related books such as Shigeru Mizuki's *Illustrated Encyclopedia of Japanese Yokai* and Katsumi Tada's *Inhabitants of the Fantasy World*, the Itsumade was given interpretations such as being "the manifestation of the grudges of the dead left unburied during wars and famines" and "crying out beside corpses to protest, 'Until when will you leave these corpses exposed?'" This can be seen as a transformation designed to make the yokai's reason for existing (grudges and warnings) more easily narrative and comprehensible to modern people, while still being based on the *Taiheiki*'s background setting of the Kenmu era epidemic.

Furthermore, Hiroari, who shot down the monster bird, is sometimes linked to the legend of "shooting the Tengu of Mount Hira." This is likely a conflation born from the similarity between "Hira-san Jirōbō," one of the eight great Tengu of Japan said to inhabit Mount Hira (Shiga Prefecture), and Hiroari's common name "Jirōzaemon," or from their equivalence as medieval tales of slaying monsters. Hiroari is said to have later traveled down to Kyushu following the Seisei Shogun, and a memorial tower attributed to him (Mayumi Tenman Shrine) remains in present-day Yamakawa-machi, Miyama City, Fukuoka Prefecture. The fact that the slayer of an anomaly that existed in literature is tied to historical sites rooted in the local region is an interesting trace demonstrating the spread of this legend.