Helck

Story:

The Demon King has been defeated and now the Demon World is running a competition to choose a successor. A muscular, high-level human named Helck has joined the competition claiming that he wishes to destroy all humans. Is he serious? Red Vamirio, one of the Four Heavenly Kings of the entire Demon Empire, is monitoring the competition and cannot trust him. What's the secret behind Helck, and the Human World?