All Lee Hongbin has ever wanted to be is a doctor, but it is difficult to become a doctor when you constantly struggle as a patient. "You're such a goody goody. Do you even remember what happened all those years ago? What happened to us? I've been protecting you all our life, but no one seems to understand that!" "You aren't protecting me, you just make everything worse!"

There has been peace between the four kingdoms for centuries. The Kingdom of the Cursed, the Kingdom of the Elementals, the Kingdom of the Divine, and the Humans have kept the peace by spreading out. Separated by huge walls and great distances, contact between kingdoms is rarely heard of.  Trouble seems to be on the horizon when at the coming of age ceremony, twelve elementals are chosen by some legendary spirits. These spirits warn the princes of Exo of the "darkness that hides within the li