When mysterious dungeons materialize, individuals with newfound abilities embark on expeditions to uncover their riches. Among them is Saeki, deemed inept due to his lack of skills. Despite this, driven by the need to fund his ailing sister's treatment, he resolves to become an adventurer. Unbeknownst to all, Saeki harbors a remarkable past as the once unrivaled mage of a previous life. Now reborn, he must progress through levels to reclaim his lost prowess. Witness the tale of an underdog set to revolutionize the realm with his burgeoning strength!