Officially, Island Zero is a no-man's land. It's at the northern tip of the archipelago of disputed islands between Japan and Russia, and is claimed by both countries.
The unofficial story is, of course, more interesting.
The day after the bombing of Hiroshima, witnesses described seeing a bright light and a terrible storm over the island. The cause of the light and the storm are still unknown - perhaps a bomb, or a mutagenic accident or a portal opened from another world. Whatever happened, five years later the island was populated by monsters.
These monsters were huge and terrifying. Three-headed dragons, fire-breathing dinosaurs, moths the size of airplanes. They had free rein on the island, but never left, and never bred. By the mid-seventies, all the monsters had died. An international guard was put on the island with an observation post to see that no one from the outside saw what was there.
In 1999, a small cult led by a charismatic Japanese writer got onto the island, with the intention of using it as their base of operations for the takeover of the nation. They were stopped by *Planetary*. At the same time, a new, living monster was seen flying over the island, suggesting that not all of the monsters died after all.