I Have My Own Dungeon To Leveling

Arthur, was stranded in this world at age 12 after learning the news of his parents falling into a coma after successfully defending the nation's borders. Learning later that an expensive magic potion is required to awaken his parents from a coma, Arthut becomes a hunter and wanders from portal to portal alongside a group of inexperienced hunters who despise him and treat him like useless garbage. After escaping piggyback from the beasts' claws during an F-rank dungeon expedition, Arthur falls unconscious due to his severe injuries. On the verge of dying due to excessive blood loss from him, he suddenly hears a monotonous voice in his head with what little consciousness he has left. [Do you wish to enter the dungeon?] Not knowing what's going on or what this voice is in his head, Arthur unconsciously agrees. After agreeing, his soul is sealed by the voice in his head and Arthur is transported to a mysterious dungeon where he fights powerful infinite beasts and in the process gains incredible strength.