Dungeons have suddenly appeared all over the world, turning ordinary people into explorers who dive into them to obtain rare resources. Kurose Sakuto is one such explorer, driven by a desperate goal: to find the legendary elixir, a medicine said to heal any illness, in order to save his childhood friend from an incurable disease. However, his companions inform him that he is no longer needed and expel him from the party. Cast out and alone, Sakuto must navigate both the treacherous dungeons and the real world, where he confronts not only monsters but also malicious humans. His dismissed status forces him to rely on his own wits and a newfound ability known as Dismantle, which grants him EX-rank power. Despite the betrayal, he continues his quest for the elixir, forming new alliances and battling increasingly dangerous foes. The story unfolds across both modern urban settings and labyrinthine dungeons, blending gritty survival with fantasy action as Sakuto fights to overcome his past and achieve his goal.