Greor

The highest-ranking demon, known as the Demon King, is such a powerful being that a Seraph had to sacrifice his own life to seal him away. Even while sealed, his curse possesses enough power to pollute the surrounding lands. Several months before Hakuto Kunai was summoned, the Demon King broke his own seal and rampaged across various regions. He demanded human sacrifices, and Aku was chosen as one of them. Aku possessed enough strength to inflict a slight physical wound on Hakuto Kunai, but ultimately, he was no match for Kunai and was defeated in an instant.