Ok, so... sorry about my poor explanation XD
It's mainly based in a school created to give a place for people with 'supernatural powers' (think like xmen, just 982358 times better) - you don't have to go to the classes, so it won't be boring. Anyway, there are demonic people from another realm called "Shurin" who appose the students at Darks. Because of this, there is a war between them.
This is based in modern times - so the humans don't know about this ^^