Satou Ryouta, a man employed as a salaryman by a company that exploits its workers, suddenly finds himself transported into an unfamiliar dungeon in a strange world where monsters drop all sorts of treasures. Luckily, he meets Emily, a girl who offers him assistance in assessing his abilities, only for him to discover that all of his physical and magical stats are ranked F — the weakest level — and he is locked at level one. These findings leave Ryouta in a state of despair, but he soon realizes that he possesses the powerful "Drop Skill: All S," which is the most potent and unique skill of all. Will Ryouta be able to survive in this fantastical world? Get ready for the thrill of the strongest and weakest adventure!