Mukashi Totta Kinezuka de... to Iinagara Musou suru Teishokuya no Ossan, Jitsu wa Densetsu no Dungeon Kouryakusha

A world where Dungeons have appeared on Earth. Kenichi Nishida, a 40-year-old man, quit his salaryman job to open a diner, but it was a total failure. After much agonizing, what he came up with was Menu development using Dungeon-sourced ingredients & Livestreaming his ingredient procurement! He breeze through conquests that would normally be life-threatening—just who is this old man!? Viewers, Idols, and even S-Rank Adventurers are obsessed with Nishida's overwhelming strength and mysterious charm!