Ano Hi Chikyuu ni Dungeon ga Shutsugen shita Ano Hi Chikyuu ni Dungeon ga Shutsugen shita

One day, a huge dungeon appeared all over the world. Amekawa Hotaru, a withdrawal high school student living in Hokkaido, is trapped in a dungeon that appears near his house. Hotaru who managed to return to the ground saw the appearance of a monster that sneaks around the world!