Ama-no-Jaku has the build of a large man with wild hair and teeth so large they appear to be protruding from his mouth.
Ama-no-Jaku is bad-tempered and overtly mischievous. He has said that seeing other people happy makes him sick. His favorite food is smoked meat and he has a smoking stove in his hideout.
Shonen Magazine / First & Second anime
The Ama-no-Jaku was sealed away inside a komainu statue 600 years ago for his wicked deeds. He was released when his seal was broken by a bitter old man and the two of them decided to cause trouble together. He and the old man go into a nearby town and refuse to pay their bill at a restaurant, and when a cop is called in on them Ama-no-Jaku easily defeats him. Soon joined by Nezumi-Otoko, the three of them then head back to the mountains to a hideout Ama-no-Jaku had built before he was sealed. The Japanese defense force attempted to investigate them, but Ama-no-Jaku scared them off by hurling trees and boulders at them, so Kitarō was called in to handle the situation. Kitarō was able to defeat him by tickling him with his Remote Control Hand while he was preparing to hurl a boulder, causing it to fall on top of him. In the anime version (1st), which did not include Kitarō's Remote Control Hand ability, Kitarō instead lures him into a nearby pond, where the weight of the boulder causes Ama-no-Jaku to sink into the mud. Kitarō and Nezumi-Otoko then placed the Komainu statue on the new boulder, sealing Ama-no-Jaku once more.
He later testifies against Kitarō at The Great Yōkai Trial, going along with Momon-Jii's scheme in order to get back at Kitarō. In the Second anime, he also takes part in the party Momon-Jii secretly arranged to have filmed, drinking sake with him and Miage-Nyūdō. He is defeated along with the other cohorts by the Kitarō Family after Kitarō is pardoned and released.
In the third series his story went pretty much the same as the original manga, although he and the old man were shown cause far more mischief around the town. During the fight wwith Kitarō, Konaki-Jijii sets off a bomb, causing an avalanche to bury Ama-no-Jaku under a pile of rocks. Kitarō places the Komainu statue on the pile to seal Ama-no-Jaku away.
In this adaptation, he was not included in the Great Yōkai Trial.
In the fourth series he is freed by Nezumi-Otoko and kidnaps a young girl named Yurika in order to eat her for his first meal in 500 years. In his fight with Kitarō, he ends up in a test of strength with Nurikabe. Nezumi-Otoko, Neko-Musume and Yurika then work together to shove the stone waterwheel on to him from above. He is able to hold it up for awhile, but Konaki-Jijii jumps on top and weighs it down, crushing him into the ground. They then place the statue that kept him sealed originally on top of the waterwheel.
He is later seen among the crowd of evil yōkai witnessing the Great Yōkai Trial but does not play an active role in the events.
In the fifth anime he appeared as a team with Te-no-Me. They help Momon-Jii frame Kitarō for the Great Yōkai Trial by stealing all of the Tsurube-Bi of Yōkai Yokochō. The Kitarō Family eventually capture and expose them, exonerating Kitarō.
In episode 88, they try to kill Kitarō by severing his lifeline while he dangling over the pits of Jigoku during the Jigoku Quiz. Kitarō's friends save him, however, and because Enma-Daiō saw the whole thing happen, the two are sentenced to be boiled in a giant pot of water.
Ama-no-Jaku is known as the Awoken Monster (さとりの怪, Satori no Kai), as he is capable of quickly sensing the presence of his enemies. He has some telepathic powers as well, as he was able to enter the mind of the old man who found his prison, convincing him in his dreams to undo the seal. In the 3rd anime, he can also read other's minds.
Immense Strength: He is as strong as thousand men and is powerful enough to stop moving vehicles. In the 4th anime he is strong enough to endure a test of strength with Nurikabe.
The Ama-no-Jaku is typically portrayed as an impish demon who can manipulate people into acting on their darkest desires. It is also a figure in Japanese Buddhism, representing wickedness. It is often depicted being subdued into righteousness by the god Bishamonten.
One story of the Ama-no-Jaku sees it killing a young girl named Uriko-hime and impersonating her by wearing her skin.