Story

Note: This summary is based on what I know from watching Frontier so it may be accurate or in-accurate to what other people have written.

Long ago in the Digital World, there existed two types of Digimon, the Human Hybrids and the Beast Hybrids. Both sides disliked the other and constantly battled one another to see which side was the strongest. Eventually, a Digimon named Lucemon appeared and was able to stop the fighting between the two sides and took his place as ruler of the Digital World.

However, over time he became corrupted by his new power and control and eventually rebelled thus starting a new war between the hybrids. 10 Digimon, known as the Legendary Warriors of Fire, Light, Ice, Wind, Thunder, Earth, Wood, Water, Steel and Darkness defeated Lucemon and imprisoned him so that his power would be contained. Their mission completed, the 10 released the spirits that they had and the 3 Great Angel Digimon Seraphimon, Ophanimon and Cherubimon were put in charge of the Digital World and ruled it as a counsel ever since.

Yet, it was not to last. Cherubimon, who was the only Beast Angel of the three wheras Seraphimon and Ophanimon were Human Angels began to feel that his fellow rulers were rejecting his ideas. Eventually, he became corrupted and turned to the dark side and waged a war with the other rulers. Seraphimon was badly wounded in the battle and Ophanimon who begged Cherubimon to spare him became his prisoner in the Rose Morning Star while Seraphimon was imprisoned in his castle at the Forest Terminal.

Cherubimon wasn't done yet for he found 5 of the 10 legendary warriors spirits. Four of those spirits were created into Digimon, Grumblemon who had the Earth spirits, Arbormon who had the Wood spirits, Ranamon who had the Water spirits and Mercurymon who had the Steel spirits.  The spirit of Darkness was given to a boy named Koichi who had found his way into the Digital World. Cherubimon sensed the darkness in Koichi's heart and gave him the human spirit of darkness and corrupted him into being his last warrior.

As a final means of help, Orphanimon called out into the Real World and asked for 5 kids who could help save the Digital World. Takuya, Koji, J.P, Zoe and Tommy arrived in the Digital World and proved to be the ones who were destined to find the remaining spirits and save the Digital World. Thus the story begins....