Kazuhiko Ezoe who runs a administration session agency in Edogawa, Tokyo lives a care-free bachelor life when he all of the sudden unintentionally activated a dungeon whereas investigating a wierd gap that appeared in his backyard. Finally, dungeon begins showing all around the world and every of the nations’ authorities started to think about on find out how to make the most of them.Nevertheless the dungeon has a critical secret. If issues proceed as it's a monster flood would happen and 10 years’ time and destroy the world.