The first story focused on Tai and Kari Kamiya four years before their adventure in the Digital World. It shows their first encounter with Digimon and what happened to them (as well as the other children). Tai and Kari wake one morning to find a Digi-Egg that came out of their computer the night before and the egg soon hatches, revealing a Botamon. The Digimon then evolves into Koromon and then Agumon (not the same one that became friends with Tai in the series, and yet, somehow, both Koromon and Kari remember each other), who then goes out and unintentionally destroys a good part of the neighborhood with Kari riding on his back. A second Digi-Egg appears in the sky to reveal an evil digimon, Parrotmon. Agumon then Digivolves to Greymon but isn’t strong enough to beat Parrotmon and is knocked out. Tai grabs Kari’s whistle and wakes up Greymon, who defeats Parrotmon and disappears with him.

Civilization has been destroyed by war and pollution, but the survivors have built the last city of Ecoban. As most natural resources have been exhausted, Ecoban is powered by pollution. The citizens of Ecoban need to continue creating this pollution leading them into conflict with the inhabitants of Marr while one man just wants to clear away the clouds and see the sky.