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! ___ * [Japanese Web Novel](https://ncode.syosetu.com/n0206fc/)