Oni

Oni are generally jolly and love to drink, feast, and compete with humans in any kind of contest, from simple physical fighting to drinking games. Long ago, when an oni found a human that they liked, they tempted that human into challenging them in any way the human desired. Should the human lose, they were abducted. Because normal humans were nowhere near an oni's level of ability, humans resorted to sneaky underhanded tactics in order to beat the oni. Tired of being tricked and killed all the time, the oni swore off humans forever and left for a place beyond human reach, or so the legend says.

In Gensokyo, the oni were once the main residents of the Youkai Mountain, and were above the other races such as tengu and kappa in the hierarchy. They were led by the Four Devas of the Mountain. However, they eventually moved into Former Hell after Hell was moved away from the Underworld by the Yamas. Other youkai moved to the current Hell as well.