Randan

Randan (ランダン) is the leader of Four Heavenly Kings. He is a human in appearance. He is advised (perhaps bullied) by his lead advisor Bizel.

Since the appearance of the Hiraku Machio after killing a rogue Wyvern. He been fearful for his life, since takes incredible power for single person to kill such a creature. Then further realizing how dangerous the Taiju Village truly is with all it's unique residents, including the Demon Spider Zabuton whom fought his predecessor 100 year prior to a draw.

In Chapter 136, It is revealed that he is not the Demon King, but rather the leader of Four Heavenly Kings.