Maou to Yuusha ga Jidai Okure ni Narimashita魔王と勇者が時代遅れになりました@COMIC; The Demon King and the Hero Became Out of Time

A young guy named Igusa, obsessed with all things evil, gets reincarnated as the Demon Lord he always admiredonly to end up in a seriously rough situation. The new world hes 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, its already on the verge of collapse Thats 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. Hell 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!