Kikakugai no Dungeon Kouryakusha, Jitsu wa Isekaigaeri no Moto Yuusha

In a modern world where dungeons have appeared and gifted individuals make a living clearing them, Rento Yuuki—a former hero who defeated the demon lord in another world and returned home—is worn out from fighting and wants nothing more than a peaceful life of nonstop gaming. But when an old friend sees through his disguise and drags him into dungeon raids, word of his off-the-charts power spreads like wildfire... "At this rate I won't even have time for dating sims!" Will Rento ever get the quiet life he longs for?! An exhilarating low fantasy about a hero who once saved another world cutting loose with power beyond measure!

(Source: Funguild)