Hoegwihan Mawangeun Chakage Sanda

"Demon King Zeke Mohr, become someone who does good in your next life!" The hero shouted to the Demon King of Power, Zeke, as the Demon King met his demise. When he opened his eyes again, he found himself back as Zeke Steelwill, before he became the demon king. He had no desire to become the successor or the Demon King in this life. Then what? Yeah! Maybe I’ll do "good" like that hero said! But how do you do that? The former Demon King of Power was unfamiliar with the concept of "kindness."

(Source: mangaupdates)