Kazuhiko Ezoe who runs a management consultation firm in Edogawa, Tokyo lives a care-free bachelor life when he suddenly unintentionally activated a dungeon while investigating a strange hole that appeared in his garden. Eventually, dungeon starts appearing all over the world and each of the countries’ government began to consider on how to utilize them. However the dungeon has a serious secret. If things continue as it is a monster flood would occur and 10 years’ time and destroy the world.