Dungeon no Sokuryoushi: Chizu de Musousuru Dungeon Kouryaku

The "dungeon map" is indispensable for conquering dungeons, but who exactly drew it? Dalia, an E-rank "dropout" hero, aims to conquer a high-difficulty dungeon that lacks a map, only to find herself wandering aimlessly. Into this dungeon, teeming with dangerous monsters, a man collapses. Though he claims to be suffering from nothing more than a hangover, this middle-aged man is actually Graham, the legendary hero who came closer than anyone else in history to defeating the Demon King. And in his hands, he holds a sheet of paper and a pen...