Satou Ryouta, a salaryman working for an exploitative company, suddenly finds himself inside an unfamiliar dungeon in a strange world where monsters drop all sorts of items as loot. With the help of a girl he happens to run into named Emily, he's able to check his own stats... and finds that all of them, both physical and magical, are at rank F (the weakest)! What's more, his level is stuck at 1 (the lowest)! Ryouta is on the verge of utter despair... but then he learns that he also has "Drop Skill: All S," the most powerful unique skill there is! Can Ryouta manage to survive in this bizarre world?! The strongest and weakest adventure of all is about to begin!