Isekai Saikyou no Daimaou, Tensei Shi Boukensha ni Naru is a Manga/Manhwa/Manhua in (English/Raw) language, Action 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

Lucifer, the greatest demon lord, who saved the demon race in the war with gods, is reincarnated as a normal adventurer.