Sanmoto Gorōzaemon is a demon king from a 1749 Japanese ghost story. He spent thirty nights trying to frighten a teenager out of his own house, and lost. On the last night he finally explained why. He had made a wager, demon lord to demon lord, and the lord on the other side of that bet was named Shinno Akugorō (神野悪五郎). In most versions, that mention is the whole of his part. Shinno Akugorō never speaks. He is named by his rival, and the story moves on without him.
What does Shinno Akugorō look like?
No one can say for sure. Most scrolls of the Inō Mononoke Roku, the record of that haunting, never show him. One scroll, the Inō Budayū Ichidaiki, has Sanmoto offer to bring him. A half-visible figure in court dress then appears. Other scrolls call that same figure the boy's guardian god. Scholars think the Ichidaiki text simply got muddled.
Even his name refuses to sit still. Surviving scrolls spell it several ways: 神ン野悪五郎, 真野悪五郎, 真の悪五郎, しんの悪五郎. These small variations were picked up as scribes copied the tale by hand over the decades. His rival's name changed too, but Shinno Akugorō's grip on his own identity is looser still.
His given name reads like an ordinary man's name from the Edo period (1603–1868): 神野 (Shinno) as a surname, 五郎 (Gorō) as a first name, the kind of name a real merchant or samurai might carry. One character breaks the pattern. 悪 means "evil," sitting where a polite word would usually go. It is the only hint, in the name itself, that something is wrong with this particular Gorō.
The wager for the demon crown
The Inō Mononoke Roku explains the terms just once, near the end. Two maō, or demon lords, had a running contest. Whichever one frightened one hundred brave boys first would become head of the demon kings. Sanmoto Gorōzaemon had reached eighty-five. The boy Inō Heitarō, who endured all thirty nights without fleeing his house, would have been his eighty-sixth. Heitarō's calm broke the count instead. That single failure is what the wager with Shinno Akugorō cost him.
Named, but absent
This is the strange part. Shinno Akugorō set the terms of a contest that produced thirty nights of hauntings, a floating severed head, and a boy's entire summer. None of it happened in front of him. Sanmoto Gorōzaemon does all the appearing: he arrives on the final night as a samurai in formal dress, then leaves with a vast retinue of lesser yokai. Before leaving, he hands Heitarō a wooden mallet and a warning. If the other demon lord ever comes looking for him, Sanmoto says, strike the mallet and help will arrive. Shinno Akugorō is turned, in that one line, from an absent name into an unfinished threat.
Where it comes from
The Inō Mononoke Roku records real names and a real date: Miyoshi, in Bingo Province (today's eastern Hiroshima), in 1749. It is one of Edo Japan's kaidan (ghost stories) written as if it truly happened, and it survives only in hand-copied texts and picture scrolls. Shinno Akugorō rides along in every copy as a name in someone else's mouth.
A separate, later document gives him more shape than the ghost story ever did. The Ikyō Bibōroku is an occult notebook from the Meiji era (1868–1912), compiled by the Shinto priest Miyaji Suii. It lists thirteen lords said to rule the demon realm. Shinno Akugorō appears sixth in that ranking, under a fuller name: 神野悪五郎日影. The same notebook says he sometimes visits Mount Hikuma, the Miyoshi hill where Heitarō's trouble began. Near its summit, a glowing object was said to sit atop a great cedar. It is a different tradition, written well after the Miyoshi haunting, but it does something the original tale never bothers to: it gives the absent rival an address.
Shinno Akugorō today
The Miyoshi Mononoke Museum opened in Hiroshima Prefecture in 2019, built around the yokai art collection of Yumoto Kōichi, a yokai researcher and collector. The Inō Mononoke Roku sits at the center of its exhibits, with reproductions of the scrolls that recorded Heitarō's thirty nights. Shinno Akugorō rides along there too, as the rival in Sanmoto's wager.
