In Tokyo's Edogawa Ward, Kazuhiko Ebue, a management consultant enjoying a carefree single life, unwittingly awakens a dungeon while investigating a strange hole in his backyard. Soon, dungeons appear worldwide, and nations begin exploring their uses. However, a grave secret lurks: a "monster invasion" will destroy the world in 10 years, and only the protagonist, who activated the dungeon, knows. Amidst global intrigue, a 40-year-old man gathers allies to challenge the dungeon and save the world, becoming known as the "Dungeon Busters."