In the universe long time ago, there used to be the race of the wisest being known as "Eden" who successfully created the way to link planets from the various galaxy in the universe with "The Gate of Eden," which used the power of the "Key Maidens" to lock and unlock the gates that chained the planets in the universe that have lifes, with the hope that every being in it can befriend others. However, after the highest and the wisest elder passed away, the race was divided into two groups: Black and White Eden, saperated by different beliefs and discrimination upon another that existed for over millions years. They then spent more than thousand years battle each other in the endless war for something the wise men from the past considered stupid and cruel: power.
One day, the leader of the White Eden discovered a prophesy the last elder of Eden wrote before he passed away, saying of the legendary "Universal Hero" carrying "Unversal Equipments" from somewhere in the universe was destinated to stop the war betweeen the two races and bring an eternal peace. Fearing the downfall of his own kind, the White Eden expends the war into the neighbor planets, which the act is ultimately against the law. They starts killing any possible hero and capture children and women that has any sign of being a hero or a key maiden. Choas approached every planets in the unverse, and only the chosen one can stop this nightmare.
The planet Metazoa, the planet with anthropomorphic animals as its inhabitants, is facing its downfall as the White Eden, under the name "Order of Eden," attacks and wipes out the population of the planet. The last hope of Kingdom Grandina, Prince Edrick and his fiancee/right hand woman, Sorcha, rush into the a battle against the enemy. But upon the confrontation with Cagnazzo, the Archfield of Water, they are totally defeated. In the blink of life and death, the mysterious ligh warped the prince away from the battle field where no one can find him. Poor Princess Sorcha, whose heart is broken, gets captured by the enemy, get abused, and ends up as a mental ill woman.
The prince is brought across the galaxy and landed upon the planet Gaia (Earth,) but unfortunately, he is turned back into an infant and lose all his memories. Two formor adventurers find him at the caved in gate of Eden, and adopt him as a son.
When the prince turns nine, he is a skilled swordsman who is trained directly by his father, but rather a quiet person. He and his close friend Ritz are seen wandering into dangerous places to help tose in need. In the one fateful day, however, everyone except the prince who is getting a common cold go to a school field trip, and gets ambushed by the White Eden. The prince's best friends, Ritz, Satako the robot, Rei the PA, and his mother are all captured by the evil White Eden.
In despair, the prince's father decides to seach of the way to rescue his wife. the prince and Rex, his younger brother who the prince has a rough relationship with offer themselves to join their father into the quest. The prince and Rex finally gets along after a bit of the quest, but very soon before the party faces Milon, the Archfield of Earth, and that's when everything goes to hell. The father kills the enemy along with him, Rex is captured, The mother is turned into a stone, though the prince is rescued in time by a young female Black Eden and is taken to her realm.
10 years after, the teenaged prince, who is now emotionally healed (somehow,) and Iiana, an innocent female who doesn't know the true nature of wars are assigned by the queen of the Black Eden to find the legendary "Universal Hero" and "Univeral Equipments" to defeat the evil White Eden once and for all by traversing though the planets after planets linked with the Eden Gate. The prince plans to use this opportunity to fufill the promise he had with his father and rescue the people important to him. Along the quest, the prince reunions with his old friends and rivals include Furio the hot blooded scientist, Ritz the summoner, Satako the axe user, the mage lancer Sorcha, the healer Meda, and Baan, a martial artist who is strangely resemble his long lost brother in an appearance. Together, they have to find the Universal Hero, unfold the secret of the prophesy of the Eden's wise men as well as to rescue those who are captured and abused by the White Eden, and stop the overlonging unwanted wars once and for all.