The Demon King and the Hero Have Become Outdated is a Manga/Manhwa/Manhua in english language, Action series, english chapters have been translated and you can read them here.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

A young guy named Igusa, obsessed with all things “evil,” gets reincarnated as the “Demon Lord” he always admired—only to end up in a seriously rough situation. The new world he’s reborn into has been wrecked by an interstellar war, leaving both swords and magic in decline! He finally becomes the Demon Lord, but the planet he was supposed to conquer? Yeah, it’s already on the verge of collapse… That’s when a girl calling herself a “Hero” and a beast-eared girl from another world show up. Without hesitation, Igusa forces them into his ranks, grinning like a true villain. —No land left to conquer? No problem. He’ll just take over the entire universe! A dark fantasy filled with interstellar intrigue, where Igusa and his fated companions charge forward in pursuit of “evil!”