Henri Cleats is an adventurer in a fantasy world where dungeon exploration determines a person's worth. His only skill is Evasion, considered utterly useless, and his attack power is pathetically weak. Desperate to earn money to care for his sickly younger sister, Colette, he endures abuse and ridicule from his party members until he is eventually expelled.

With no other options, Henri ventures alone into a dungeon expecting to die. During a desperate escape from monsters, his Evasion skill activates in an unexpected way, revealing a hidden bug within the ability. The skill allows him to phase through solid walls, bypassing bosses and all dangers to reach the deepest treasure room instantly. Even more remarkably, he discovers he can exploit this bug to claim a dungeons First Clear bonus, a reward normally obtainable only once, an unlimited number of times.

Using this glitch, Henri begins to amass wealth and rare items, pulling himself from the depths of despair. His life changes further when he encounters a mysterious unnamed entity residing within his sister Colette and a young magician girl named Ouroia. With his newfound ability to bypass the rules of the world, Henri takes on the powerful tyrant Guillermo, one of the titans controlling the town of Garabozo. His actions disrupt the power balance of the entire town, forcing him to grow beyond a simple bug user as he confronts greater threats and uncovers the true nature of the glitch that lets him slip through the walls of reality itself.