I think you mean Yokai, not Onis. Oni is the ogre with a horn and tiger cloth, while the yokais are all mythical beasts from the japanese folklore. But I wouldn't limit pokémon to be inspired from just the japanese culture, there seems to be a lot of influence from other mythologies, like the chinese one ( Arcanine ), norse, and so on.
That's the word I was looking for. I realize that Arcanine is a shishi lion dog but I was referring to a majority of them. On bulbanews theres a segment called origin of species that some people on here are familiar with. 7/10 of the pokemon are based on the japanese mythology including Dunsparce and Slowking being vicious creatures (Slowking's mythological counterpart cuts off male genetalia) so I was referring to that aspect.