Return of the SSS-Class Demon Lord is a Manga/Manhwa/Manhua in english language, Manhwa series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

Return of the SSS-Class Demon Lord Synopsis: A man who fell into the demon world returns to Earth as the most powerful demon lord with absolute power. However, what awaits him are mysterious monsters. Slash! Blood stitches the air, and the man’s voice echoes once more. “I’ve finally returned.” The Demon Lord’s return to Earth marks the beginning of the ultimate battle!