Salaryman ga Isekai ni Ittara Shitennou ni Natta Hanashi

In an alternate fantasy world, the Demon King reigns with a formidable army led by his Four Heavenly Kings. One happens to be Uchimura Denosuke, a normal salaryman unexpectedly plucked from his mundane life by the Demon King himself. But even in this new realm, Uchimura is bestowed no particular powers. Can he survive treacherous missions with only the knowledge of an office worker?

(Source: Crunchyroll)