Every culture has its folklore about inhuman creatures, and in Japan these are the youkai (also yōkai). There are thousands of these entities, with diverse personalities and habits, from tiny spirits which live in wild grasses or appear only as lights on tree branches to enormous monsters which might crash through your roof at night.
Just as cryptids in western lore are often regional—you would not expect to find a Sasquatch and a Chupacabra in the same neighborhood—youkai tales are often rooted in one place or another. Still, the modern age has seen some myths separate and recombine. While China, Korea, and Japan all have traditions of shape-shifting foxes, for example, these foxes traditionally had different patterns of behavior—but by the twenty-first century, we see those traditional lines blur in modern storytelling. With thousands of years of youkai tales, there has been plenty of time for cross-pollination, variation, and modernization.
The most difficult barrier for someone new to youkai stories is the question of translation. Unfortunately, a few poor translations somehow became traditional, despite being confusing or even misleading. For example, the word “youkai” itself is nearly always translated into English as “demon,” bearing religious and cultural baggage. Youkai are most simply “something that is not human,” which leaves a lot of room for not being a demon! Remember, youkai can be friendly or mischievous or tricky or murderous—one may be a physical manifestation of the rage of a massacred army, or one may be a conglomeration of broken crockery protecting your home while you sleep—so it’s inaccurate to use a word which suggests only a malevolent aspect.
I recommend that readers or viewers back-translate “demon” to “youkai” to get around the inappropriate cultural baggage—or, if an English word is truly necessary, I suggest “elf.” We have already diluted the meaning of elf in our culture, with elves who make weapons for Norse gods, or elves who help Santa, or elves who live underground and fight with scimitars and panthers, or elves who live in trees and bake cookies. It’s a word which now carries a wide variety of interpretations for creatures who live near humans but are not humans, making it a far more suitable reference than demons.
Likewise, goblins live underground and are greedy beasts, while tengu live in trees and protect their mountains from harm, so the common translation of “tengu” to “goblin” leads to confusion. Back-translation is key for anyone who truly wants to learn more about Japanese folklore.
Our fascination with the supernatural never leaves us, even as culture shifts to adopt new fears and new ways to assure ourselves we’re not afraid of the old ones. Where Americans had Casper the Friendly Ghost, Japan had Obake no Q-Tarou. While kitsune, tengu, tanuki, and other popular youkai still regularly appear in eastern and western stories, most Americans will meet the less famous youkai as Pokémon! Many of the “monsters” found in the Pokédex are traditional youkai with the serial numbers filed off, giving these folkloric creatures a new home and new life in modern story.