The first story focused on Tai and Kari Kamiya four years before their adventure in the Digital World and before they met Pooh and his friends. 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.
Our War Game:
About six months after the Digidestined departed from the Digital World, Izzy Izumi discovers a virus on the Internet infecting a Digi-Egg, then rushes over to Tai's house to inform Tai about the newly-hatched Digimon. Tai and Izzy use Tai's dad's computer and monitor the Digimon until Gennai appears in a transmission from the Digital World. He sends Agumon and Tentomon to help stop the corrupted Digimon, Keramon. They put up a good fight until Keramon Digivolves to Infermon and defeats them. Tai tries furiously to contact and alert the rest of the Digidestined and ends up getting only Matt Ishida and his brother T.K. Takaishi. They find a computer in a barber shop and upload Gabumon and Patamon onto the net. Infermon Digivolves to Diaboromon after Agumon and Gabumon Warp Digivolve to WarGreymon and MetalGarurumon but then they slow down because of the massive amount of e-mails being sent to Tai and Izzy. Tai slaps the computer and freezes it leaving WarGreymon frozen and defeated. Diaboromon then starts multiplying and sets up a timer for 10 minutes as he forces the Pentagon to launch two nuclear missiles: one headed for Colorado, the other for the neighbourhood in Odaiba, Tokyo, where Tai currently lives. WarGreymon and MetalGarurumon wake up and race to defeat Diaboromon, only to find over a million copies of him. Every single copy fires and blast them until they lie defeated. Tai and Matt's bond to their Digimon is so strong they become digital and enter their computers and talk to their Digimon. Giving them words of hope and strength and the kids around the world doing the same to them. WarGreymon and MetalGarurumon DNA Digivolve to Omnimon who easily defeats all but one Diaboromon. At one minute to go, Diaboromon is still too fast for them to hit, but then Izzy forwards him the e-mails, slowing him like it did to the other Digimon. At the very last second, Omnimon impales Diaboromon through the head, disabling the missiles and killing Diaboromon. But the virus tracks down Willis and infects Kokomon.
This part features the characters in the second season (and is canon to the second season since it takes place right after the Digimon Emperor was defeated). It starts out with T.K. and Kari (visiting Mimi in New York) taking a picture, but having trouble, and then Kari senses something. They end up briefly meeting Willis and Terriermon, who are engaged in a battle with Wendigomon, Kokomon's corrupted Champion form (still referred to as Kokomon), who keeps telling Willis to "go back", and then vanishes. Willis and Terriermon travel to Colorado while Kari, on a train with T.K., e-mails Davis Motomiya to inform him of Willis and Kokomon.
After taking planes and taxis, Davis, Yolei Inoue, and Cody Hida end up meeting Willis in a truck while Kari and T.K. literally get derailed by Wendigomon. Willis tries to get Davis, Yolei, and Cody a lift to his house. The ride leaves without Willis and Davis, who encounter Wendigomon which leads to a battle between Davis, Flamedramon, and Gargomon, Terriermon's Champion form. Before anyone is defeated, Wendigomon vanishes again, repeating his cryptic message, "go back". Davis and Willis meet up with Yolei and Cody who told Davis that T.K. and Kari aren't there yet. Willis doubts that they'll come at all if Wendigomon interfered. After the kids question his knowledge about Wendigomon, Willis reveals that he created him but regrets saying so and storms off, while being followed by Davis. Willis reveals the story about Wendigomon, how he became infected, and reveals that he was the one who basically created Diaboromon. Davis tells Willis how they're part of a team, and that he doesn't have to face Wendigomon alone. Terriermon overhears the conversation (blaming it on his "really big ears") and says that he's "not Willis's pet, but his friend", and wants to be beside him every step of the way. Willis refuses his help out of concern for his safety, but Terriermon talks him into letting him battle. At Willis's home, Wendigomon reappears, as expected, but Digivolves to Antylamon. He swiftly evades the attacks of Gargomon, Flamedramon, Halsemon and Digmon and throws all the Digimon around like rag dolls. Antylamon Digivolves again into Cherubimon.
However, they still try to fight, but don't prevail, as Cherubimon grabs them and is about to eat them when Angemon and Angewomon cut off his arms and T.K. and Kari show up. Cherubimon de-Digivolves the Digimon then de-ages the Digidestined, revealing that he wanted Willis to "go back" in time to when the virus first attacked him. Angewomon and Angemon Digivolve to their Mega forms, Magnadramon and Seraphimon, to release two Golden Digi-Eggs for Willis and Davis. Veemon and Terriermon Golden Armor Digivolve to Magnamon and Rapidmon who go into Cherubimon. Inside they see Wendigomon who tells them to destroy the virus. Doing so purifies Cherubimon, who soon dies. After saying goodbye to his new friends, Willis and Terriermon walk back home, and notice the Digi-Egg that will hatch into Kokomon. The film ends with Kokomon having Digivolved back into Wendigomon, who begins to dance tone-deafly.
- Ash Ketchum, Pikachu, Misty, Togepi, Brock, and The Masters of Evil will guest star in this film.
- During the third act, the Four Evil Legendary Warriors will be manipulating Cherubimon into conquering both worlds instead of the other way around just like it was in Digimon Frontier.
- Both The Tigger Movie, Pokémon 2000: The Movie, and Digimon: The Movie were released in 2000.