Long ago, a group of ten Digimon sacrificed themselves to defeat a ultimate evil that threaten the Digital World. These Ancient Warriors created artifacts from their data, the twenty "Spirits", before leaving the Digital World in the care of the three Celestial Digimon. However, one of the three, Cherubimon begins a reign of terror. To counter this, the Celestial Digimon Ophanimon summons five children from the human world into the Digital World via the train-like Trailmon. There, these five Digi-Destined find their repective Human Spirits and "Spirit Evolve" into Digimon, the Legendary Warriors. However, while finding their respective Beast Spirits, the five find themselves hunted by five other Legendary Warriors that serve Cherubimon.
After they defeat four of the them, Koji Minamoto discovers that Duskmon, the fifth evil Legendary Warrior, is really his twin brother Kouichi Kimura. With Takuya Kanbara's help, Koji is able to free his brother, and Kouichi restores the Spirits of Darkness to their true forms and joins the team as the true Warrior of Darkness, Löwemon. After they defeat Cherubimon, the Digi-Destined learn that the true mastermind was the very evil the Anicent Warriors sealed away within the Digital World's core, Lucemon. So now the six Digi-Destined must try to defeat the two Royal Knights before they scan all of the Digital World, senting it to Lucemon to complete his rebirth.