Helck

Helck (ヘルク, Heruku) is a manga written and illustrated by Nanao Nanaki and follows the adventures of Helck and Vamirio. The manga is published by Ura Sunday and has several volumes to its name.

Plot
The Demon King has been defeated, and now the Demon World is running a contest to choose his successor. A muscular and high-level human named Helck has joined and says that he wants to destroy all HUMANS. Is he serious?

Red Vamirio, one of the Four Heavenly Kings of the whole Demon Empire, is monitoring the contest and can't believe this. What's the secret behind Helck and the human world?