"Welcome to the royal capital of Glendeer!"The protagonist works as a "gatekeeper" in the royal capital of Glendeer. However, he is fired from his job for an unreasonable reason. The "gatekeeper" leaves the country without knowing that he has become the strongest by hunting vicious monsters in the sewers of the royal capital... Because of his strength, he makes a cute apprentice and saves many villages from crisis, but he mistakenly believes that it is not his own ability!? No matter how great his achievements are, he insists, "I'm just a gatekeeper." The adventures of this extremely air-headed gatekeeper, whose misunderstandings lead to more misunderstandings, begin!