In this world, Rankers with various magical powers contracted with spirits battle monsters from invading humanity. But not all are lucky to be chosen Rankers, Yuuki Machida, born as a non-ranker who has barely even considered to be a human was barely able to survive and make a living.
However, on one raid he meets the devil who decides to help him hoping he can pass on the lesson to the next generation so that this hatred, anger, and resentment can be stopped so that such sadness never happens again.

The Rankers