"It has been said that the tower in the center of the World is connected to Paradise. Dreaming of a life in Paradise, many have challenged the secret of the tower, but no one knows what became of them. Now, there is another who will brave the adventure.
In the center of the world is a great tower. This tower connects to many worlds and at the top the entrance to Paradise. A group of adventurers from the world at the base of the tower decide to climb it to explore the various worlds. Along the way they encounter many strange creatures and among them strong monsters based on the Chinese Zodiac who guard the key to the next floor.
In the Base World, Gen-bu, the Black Turtle, has hidden the Black Sphere in the Statue of Hero, southwest of the Tower.
Two dragons guard the divided Blue Sphere in the World of Sea. Sei-ryu, the Blue Dragon, holds dominion over the realm from a palace below.
A resistance force builds in the World of Sky as Byak-ko, the White Tiger, rules the realm with an iron fist in search of the White Sphere.
Su-zaku, the Red Bird, lays waste to the World of Future as he guards the Red Sphere.