The yokai of Japan have a good thing going for them blending in with the humans. It would be a shame if some bad or careless people ruined it for all of them. And that is why Hatano Reformery School was created 50 years ago. While troublesome adults can be 'dealt with', tying cinder blocks to a minor's legs and tossing them into Tokyo Bay just seems cruel. So yokai youngsters who are considered an exposure risk (whether on accident or on purpose) are packed up and sent off to the secluded boarding school to learn how to better blend into human society. It has a high success rate (probably helped by the official motto of 'graduate or just die already'), but this year they're adding something new!
Humans!
No more life in an echo chamber! This year the school will let in humans to further cultural understanding and let the more unstable yokai grow accustomed to being around them in small doses before being let back out into the world again. Will this gamble pay off? The dean has bet a lot of money, so it better!