What happened? Why they're changed? Are they betrayal? How can they fight each other? Anyo...

Licht opened the gate between the human world and the elf world. All of his friends came and took over the bodies of some chosen people. (most likely people who have some connections to elfs, probably elfs themselves)

I think more than half of the royal knights are turned or chosen to be the elves, how will the rest of the royal knights be able to survive there especially most of the strong ones are down... either they themselves break through the elf side or break the rock full of magic stones or the rest of the royal knights defeat the elves ... hmmm...