A large hole in the center of Japan. It was called "The Hell Gate". Due to the appearance of the Hell Gate, there was a great natural disaster, the ground shifted, the seas created new paths, and Japan lost it's shape as an archipelago. This phenomena is responsible for the events of Big Bang Age. Within the hole there are many demons, B-crystals, and strange paranormal energy.
It is learned the Hell Gate will vanish in a few years only to move to another location. In the ending of Big Bang Age it is revealed The Hell Gate vanished in Japan in few year ago and it appeared again in Europe
(Note: The name in the translation seems to be "Hell Hole")