The Ippon-Datara (一本踏鞴*)? is a rarely spotted youkai due to its innate shyness driving it away from urban areas. Hermitting himself in the mountains of Japan, it is best known to lurk in the mountains bordering the Wakayama and Nara prefectures, though there have been sightings within their immediate neighboring prefectures. Their method of locomotion is by hopping around and doing somersaults. While normally wanting nothing to do with humans, once a year, on December 20th, if a human and Ippon-Datara meet, they will squash the humans unfortunate enough underfoot, and is such considered an unlucky day in those prefectures, and are urged to stay away from the mountains.
The Ippon-datara is said to resemble a one footed, cyclopoid blacksmith, having lost both from working his trade, being blinded by the light of his forge and working the bellows with one of his legs. Alternative theories have implied Ippon-datara's origins as a woodcutter who lopped off their leg as penance for some crime, a killer boar that attacked humans that was bound by a priest that was allowed to attack again on Dec. 20th, or a mountain kami who was corrupted into becoming a youkai, much like Nozuchi or Hitotsume-kozou.
Ippon-Datara also appears as an opponent in the Challenge Quest, "Training Battle 1." In this battle, he will alternate between using the Heat Wave and Maragi skills. Flynn, Dzelarhons, and Pyro Jack will automatically repel its Maragi attacks. As it only lasts one turn, the Tetrakarn skill needs to be reserved for turns where Ippon-Datara uses Heat Wave, otherwise the party will be wiped out. Ippon-Datara will always use Heat Wave on the first battle turn. Additionally, Flynn's gun is equipped with poison rounds, which can inflict additional damage on Ippon-Datara if he becomes afflicted with Poison status.
Shin Megami Tensei IV Apocalypse
Ippon-Datara can be found within Kanda-no-yashiro. He can bestow the Power Punch, Mudo and Oni-Kagura skills through his Demon Whisper. He receives a decent bonus to any Physical skills learned.
Ippon-Datara later becomes the focus of a quest for the Hunter Association, called "Flying Sparks, Rolling Water." Tatara of the Artisans' Union puts out a request for a hunter to bring them an Ippon-Datara, so that it may provide them instructions on smelting techniques for creating weapons.
Shin Megami Tensei V
"A monster with one eye and one leg, said to live deep in the mountains of Kumano, Japan. A single footprint measuring 30 cm has been sighted in the snowy mountains."
—Shin Megami Tensei V lore
Ippon-Datara appears as a follower of Leanan Sidhe, seeking her guidance in improving his skills in the "The Spirit of Love" subquest. If the protagonist moves to fulfill the request of Apsaras, or doesn't accept the "The Water Nymph" subquest, he will join Leanan Sidhe in fighting the protagonist and his party.
Devil Summoner: Soul Hackers
"A monster with one eye and one leg, said to live deep in the mountains of Kumano, Japan. A single footprint measuring 30cm, said to belong to Ippon-datara, was sighted in the mountain's snows."
—Devil Summoner: Soul Hackers 3DS compendium
Devil Summoner: Raidou Kuzunoha vs The Soulless Army
"A monster with one eye and one leg, said to live deep in the mountains of Kumano, Japan. A single footprint measuring 30 centimeters has been sighted in the mountain's snows."
—Devil Summoner: Raidou Kuzunoha vs The Soulless Army devil chart
He will later appear on the factory floor of the Daidouji Factory, outside of the Matrix Labyrinth.
In battle, Ippon-datara's normal attack consists of grabbing his enemy with his tongs and delivering three light hammer strikes.
Devil Summoner 2: Raidou Kuzunoha vs. King Abaddon
An Ippon-Datara serving Dr. Victor is disguised as a maid, and gives Raidou Kuzunoha the XIV the doctor's first request. He shows up later to tell Raidou about his master's new branch of Sword Fusion, while complaining about the maid outfit.
"A one-eyed, one-legged monster said to live deep in the mountains of Kumano, Japan. Believed to be the degraded blacksmith god, Ame no Me-Hitotsu no Kami."
"A one-eyed, one-legged monster said to live deep in the mountains of Kumano, Japan. It's believed to be the degraded blacksmith god, Ame no Me-Hitotsu no Kami."
—Persona 5 background
Ippon-Datara is the third Persona of the Hermit Arcana and can be found as a Shadow in Madarame's Palace and the Chemdah area of Mementos, with the title "Embittered Blacksmith." He is the second of two Personas to learn the Resist Dizzy skill and the first Persona to learn the Rampage and Counter skills. When itemized through Electric Chair execution in the Velvet Room, Ippon-Datara yields a Sledgehammer skill card.
Yasuo Jochi's Shadow takes the form of Ippon-Datara during the request "Who's Muscling in Yongen-Jaya?" Shadow Jochi waits at the end of the Path of Kaitul in Mementos.
Shin Megami Tensei: Liberation Dx2
"A monster with one eye and one leg, said to live deep in the mountains of Japan, though its appearance varies from story to story. On the snowy paths of Mt.Kumano, a trail of single footprints is the only evidence of its existence."