Throughout three different stories, Kari Kamiya and her friends take on explosive adventures involving digital creatures.
The film is an edited version of three different Japanese short films, which have been combined together. There is narration by a continuing character, Kari. The first segment of the film revolves around the first encounter with a digimon and a fight that occurs between their digimon and another. The two kids, Kari and Tai, raise a fast-growing digimon from an egg to a large, dinosaur-like digimon, which escapes from their house and then has an encounter and a battle with a parrot-like digimon. The second segment mainly involves Tai and another digiDestined friend of his, Izzy. A computer virus sweeps across the internet, effecting a digiEgg, and thus creating an infected digimon. This infected digimon begins to start eating computer information and data, and the two protagonists attempt to stop the digimon, but fail. After the infected digimon manages to get into the American information system and launch two nukes, one at japan and one at Colorado, Tai and Izzy get help from teammates Matt and his little brother T.K. They successfully overcome the infected digimon and prevent the nukes from detonating. The third and final segment involves Kari and T.K., now years older, as they see a kid and two digimon fighting whilst in New York. Kari and T.K decide to follow the child, who turns out to be the creator of the virus, and, after meeting up with friends, they manage to defeat the evil digimon, who turns out to be one of Willis' twin digimon that was affected by the virus following the actions of the second segment. Together they fight against this infected digimon, and destroy the virus that was affecting Willis' digimon.—Leo
The film is split into three acts, and narrated by one of the protagonists Kari Kamiya who has a role in the first and third act of the film. Kari gives a brief introduction to the world of Digimon, explaining the existence of Digimon, monsters that were created from computer data, and live in another dimension called the Digital World. She continues, explaining she is part of a team called the Digidestined, who are partnered with Digimon to protect the world from evil. There were only a small handful of members at first, but it is added a few members introducing a new character for the film, named Willis, who lives in Colorado. Willis has two twin Digimon named Gummymon and Kokomon, but had no other friends to rely on. This takes us into the first act, on the night in 1995 when Kari and her big brother Tai encountered their first Digimon. Kari also reveals that Willis met his Digimon on the same night.
In Highton View Terrace, Tokyo, Japan, Tai awakens in the night and finds Kari observing their fathers computer, where a large Digiegg emerges. The next day, Tai and Kari witness the egg hatch into Botamon, who quickly bonds with Kari. Tai goes to answer the telephone but the call is interrupted. Returning to the bedroom, Tai discovers Botamon has transformed into Koromon, a pink ball-like Digimon resembling a space hopper. This is a process Kari later explains as digivolving, which allows a Digimon to turn into a stronger form, which affects electrical equipment. Kari steals food from the family cat Miko, causing her to attack and scratch both Tai and Koromon. At sunset, Tai and Kari discover Koromon can speak, and he calls them his best friends.
That night, another electrical surge causes Koromon to digivolve into Agumon, an enormous but simple-minded dinosaur, who leaps out the window with Kari on his back. Tai pursues them into the night as Agumon wanders the street, scaring Kari when he starts blowing things up with fireballs. A second, enormous Digiegg appears in the sky, hatching to unleash Parrotmon, a large bird-like Digimon able to fire electrical blasts. As Tai reaches Kari, Parrotmon destroys an overpass, burying Agumon under rubble. However, Agumon digivolves into Greymon and battles Parrotmon. Parrotmon knocks Greymon out, but Tai uses Karis whistle to awaken him. Greymon leaps up and obliterates Parrotmon with a fire blast, but the attack destroys him in the process.
In narration, Kari explains that she, Tai, and six other children were amongst those who witnessed the battle and were chosen to become the Digidestined. Karis narration about the team acts as a segway into the second act, set in 2000, a year after the events of the television series Digimon Adventure.
Koushiro Izzy Izumi, a computer whiz and member of Digidestined, spots a computer virus has somehow appeared on the internet and is attacking something. Getting an image of its target, Izzy amongst thousands of others across the world, witness the virus mutate a Digiegg, causing it to hatch and become a Digimon, which addresses the world with Hello!. Across town, Tai tries to compose an apology letter to his friend Sora Takenouchi after they had a falling out, but he has difficulty deciding whether or not to end the e-mail with love or from. Kari appears, off to a birthday party, sending the e-mail to Sora behind Tais back, but Tai discovers the e-mail was not delivered.
A montage follows, showing what the eight Digidestined are up to Sora wanders the streets and checks her hair in a shop window but fails to notice the virus Digimon on a large screen, Joe Kido, the oldest of the group and voice of reason misses a train to an exam for summer school, Matt Ishida and his little brother T.K. are visiting their grandmother in the countryside, Kari attends a friends birthday, and Izzy races for Tais apartment. The eighth member Mimi is absent from home. Tai bemoans to his mother that Kari gets to eat cake and their fridge is empty, so Tais eccentric mother suggests she attempt to make a cake. Izzy appears, informing Tai of the Digimon on the internet.
In Tais bedroom, they examine the Digimon. Izzy informs Tai that if the Digimon stays online, it could wipe out all technology. Izzy reveals he got his information from Willis, who is actually a child prodigy and taking classes at college already, though Tai is unimpressed. The Digimon suddenly digivolves, now resembling a cycloptic clawed hand and it starts devouring computer data, causing prices at supermarkets to triple, causing chaos at registers. Tai and Izzy race for the Kamiya computer, with Izzy trying one of Mrs. Kamiyas beef jerky milkshakes. Izzy connects his laptop and the computer together for more power, and explains Willis attempted to get his internet provider to remove the Digimon, but they ignored the threat. Getting online, they discover the Digimon has evolved again, now the creepy-looking Keramon. Not knowing what to do, Tai states he wish his partner Agumon was there (a different character from the Agumon seen in the first act).
Agumon suddenly contacts Tai through Izzys laptop, revealing he and the other partners of the Digidestined are aware of Keramon. The Digimon are joined by Gennai, a data entity who appears as an old man. Agumon and Izzys partner, the insectoid Tentomon, agree to go onto the internet to delete Keramon whilst Tai decides to telephone the other Digidestined so their partners can help too. The attempts to phone his friends doesnt go well Joe is too busy to attend (seeing racing into his exam), Matt and T.K.s grandma is too senile to give the phone to them, Mimi is away from home and Tai only gets her answer machine, Kari is unable to come home, and Tai forces Izzy to call Sora due to their issues. Izzy calls Soras house, but she refuses to talk to Tai. Izzy tells Tai and he angrily rants about her attitude, revealing their falling out happened over a lousy hairclip. Sora checks her e-mail to see if Tai sent her anything but finds nothing.
Agumon and Tentomon arrive on the internet and find Keramon eating computer data. They attack him, but when Keramon threatens Tai and Izzy, the two digivolve into their Champion-level forms Greymon and Kabuterimon. Keramon suddenly digivolves into Infermon, an armoured spider-like Digimon that proves to be stronger than Greymon and Kabuterimon. Izzy realises he is skipping stages in the digivolution chain and is now on the Ultimate-level. Greymon and Kabuterimon try to do likewise, but Infermon attacks them mid-transformation, wounding both and turning them back into Agumon and Tentomon.
Izzy starts receiving e-mails from around the world, including one from Willis who claims the whole thing is his fault and suggests that Tai and Izzy find a way to slow down Infermon. Infermon himself sends an e-mail, which only says Hello repeatedly. Izzy spots the address, realising Infermon is hacking into the phone company and could cause them to lose their internet connection. Tai tries to call his friends but finds the circuits are busy, enraging the phone operator with his constant calls. Infermon calls and asks if Tai is his creator. Kari explains that Infermon was calling every number in the world, looking for his programmer. Izzys internet connection is cut off, forcing him to run home and fetch something, while Tai collapses on the sofa in defeat.
A news reporter announces an emergency voicemailing system issued by the government to use the phone, instructing people to leave a message than call back to pick up replies. Tai sends messages to Matt and T.K., Kari, and Sora, inviting her to come to his house so they can talk about their issues. Sora arrives but hesitates at the last minute and stomps away. Tai leaves a message for Mimi, but his mother reveals they got a postcard from Mimi, who is on vacation in Hawaii cut to an ecstatic Mimi in Hawaii who doesnt have a care in the world. Izzy returns and reveals to Tai he has a satellite uplink device which will let them hack into a military satellite system to regain internet access.
Tai checks the phone messages, discovering Matt and T.K. have left messages. Tai informs them of the situation, so Matt and T.K. rush off into town to find a computer to use. Tai and Izzy go back online and find Infermon has gone, now causing havoc in New York City. Matt and T.K. contact Tai and Izzy via a webcam, revealing they are using a computer in a barber shop, where a group of eccentric patrons watch their endeavours. Agumon and Tentomon are deployed to battle Infermon again, but are join by Matt and T.K.s partners Gabumon and Patamon. Confronting Infermon, Agumon and Gabumon immediately digivolve to their Mega-level forms WarGreymon and MetalGarurumon.
The two beat Infermon down, and Patamon tries to digivolve as well. Infermon suddenly dashes at him, digivolving into his Mega-level form Diaboromon. Diaboromon uses his extendable arms to knock out Patamon and pin Tentomon down. WarGreymon and MetalGarurumon battle Diaboromon, getting the advantage. However, Izzy suddenly gets severe cramps and runs for the bathroom, blaming Mrs. Kamiyas recipes. Matt informs Tai that the Digimon are slowing down for some reason. Tai angrily slams the computer, causing it to malfunction, and WarGreymon freezes in place. Izzy returns and has to reboot the computer. He and Tai argue but then the subject turns to Sora. Tai explains he bought Sora a hairpin for her birthday, but she took offence, believing Tai disliked her hairstyle and they fell out. Izzy is stunned by the silly reason, but the attention is drawn back to the computer, discovering WarGreymon and MetalGarurumon have been defeated.
Diaboromon sends an e-mail to Izzy, asking Who can count backwards from ten?. The Digidestined witness Diaboromon create a countdown, and then he starts cloning himself. Izzy is informed by Willis that the American governments systems have been hacked and Diaboromon has fired two nuclear missiles, possibly through Izzys satellite uplink, and they will hit their targets in ten minutes, thus explaining the countdown. The two targets are Colorado and Tais neighbourhood. Izzy explains every other country is trying to intercept the nukes, but their own missiles are made useless by Diaboromon and crash in the ocean near Hawaii.
Izzy concludes that if they destroy all of the Diaboromon clones until the original one remains, then they can stop the countdown, only to discover there are over 75,000 clones and rising. WarGreymon and MetalGarurumon decide to go after Diaboromon, and Izzy realises the e-mails he is getting are slowing down their Digimon. The Digimon race to stop Diaboromon, entering a large circular chamber where Diaboromons clones swarm. They all attack at once, easily overwhelming WarGreymon and MetalGarurumon. Both are rendered unconscious. Tai despairs and moves towards the computer, wanting to help WarGreymon. Mrs. Kamiya enters offering more juice but notices Tai has disappeared. Kari explains that Tais bond with WarGreymon was so strong, it allows him to enter the internet and become digital, the same happening to Matt.
Tai speaks to WarGreymon, encouraging him to not give up and people from all over the world are supporting him. WarGreymon and MetalGarurumon awaken, harnessing the data from the e-mails, and fuse together into one Digimon Omnimon. Omnimon easily wipes out all of the Diaboromon clones, leaving only the original, but he is so fast that Omnimon doesnt have time to aim at him. With only thirty seconds left, Izzy realises he can send the e-mails to Diaboromons address, slowing him down like they did to their Digimon. Diaboromon slows down, allowing Omnimon to spot him.
Ten seconds left, the missiles head for their targets, while Omnimon dashes at Diaboromon, running him through with his sword with only two seconds to go. Diaboromon is deleted, and the missiles land harmlessly, one crashing into Tokyo Bay without detonating. Mrs. Kamiyas cake is charred in the microwave, and Sora finally receives Tais e-mail, noting the love at the end, and makes amends with him. Elsewhere in Colorado, Willis celebrates with his Digimon, only for a strange phenomenon to appear and capture Kokomon.
The films third act takes place four years later, with the introduction of the second generation of Digidestined introduced in the series Digimon Adventure 02. T.K. and Kari are in New York with the intent on visiting Mimi, but Kari senses a strange feeling in the air. Nearby, the teenage Willis flees from Kokomon, who has digivolved into an enormous ape-like Digimon (actually called Wendigomon, but he is only called Kokomon throughout the film). Kokomon cryptically informs Willis to go back and to destroy. Gummymon has digivolved into Terriermon, a floppy-earred Digimon who looks more like a rabbit than a dog. Kokomon and Terriermon fight in the back alleys of Manhattan, until Kokomon defeats his smaller twin.
Willis tries to get more information from Kokomon, but he disappears into mist. Kari, T.K., Gatomon and Patamon witness the battle but Willis flees when they call out to him. Patamon follows Willis, witnessing him call his mother at a payphone and learns he is going to Colorado. The Digidestined head to Colorado on the train, Kari deciding to contact their friends for backup. On a beach, Davis Motomiya, Yolei Inoue, and Cody Hida, along with their partners, DemiVeemon, Poromon, and Upamon, learn of the situation but are hapless on how to get to America. T.K. and Karis train is suddenly attacked by Kokomon who causes the train to halt in the middle of nowhere, warning them not to interfere.
Meanwhile, the others arrive in America and get across country by hitching rides with Yoleis large number of uncles who happen to live in the United States including a reckless cab driver, and a pilot who drops them off in a delivery plane. Davis eventually gets fed up with the travel and shouts, alerting a truck driver who pulls over, and the group hitch a ride on the truck. Inside the trailer, they meet Willis and Terriermon. A little later, the group accompanied by Willis and Terriermon, stand on the roadside. Willis is thrilled to meet other people with Digimon and flirts with Yolei. Davis is impatient to reach Kari, and Willis suggests waiting for them at his summer home in Colorado, calling a pizza delivery guy he knows to pick them up. The delivery man arrives moments later, but he drives off before Davis and Willis can get on.
Kokomon materialises, Davis sending DemiVeemon to attack him by digivolving into Veemon. Veemon, Davis, and Terriermon try to fend off Kokomon by flying at him, but crash into a billboard. Veemon digivolves into Flamedramon, but Kokomon easily defeats him. Willis tries to reason with Kokomon, who tells him to go back to the beginning. Willis Digivice, which can be used to help a Digimon digivolve, springs to life, allowing Terriermon to digivolve into Gargomon, a large rabbit who has gun turrets attached to his arms. Gargomon battles Kokomon and defeats him, but he disappears. Willis worries that Kokomon will hurt Davis and the others, but Terriermon tells him that they are a team.
Needing transport to reach Yolei and Cody, Veemon digivolves into Raidramon, and they race across Colorado to Willis summer house. Realising T.K. and Kari havent arrived yet, Willis guesses Kokomon likely stalled them. Davis, Yolei, and Cody ask Willis how he knows Kokomon, but he gets upset and leaves, followed by Davis. By nightfall, the two have been wandering for hours and Davis asks Willis what he is afraid of. Willis reluctantly explains that after he got Terriermon and Kokomon, he got the idea to try and create his own Digimon on the internet, but it was attacked by a virus and mutated into Diaboromon. But while Diaboromon was destroyed, the virus survived, somehow appeared in the real world and infected Kokomon, turning him into his present self, and he is obsessed with chasing Willis. Willis assumes that Kokomons cryptic words are about going back to where the virus attacked him, but he cant be sure. Davis encourages Willis to join their team, further supported by an eavesdropping Terriermon.
The next day, the Digidestined go to the field where Kokomon was infected, and the big ape arrives. Willis asks him what he wants but Kokomon is unable to speak anything other than Destroy! He suddenly digivolves again, becoming Antylamon, a tall rabbit-like Digimon. Veemon, Terriermon, and the evolved Hawkmon and Armadillomon digivolve to battle Antylamon. Gargomon and Flamedramon corner Antylamon, but he sinks beneath the river and disappears. Antylamon digivolves and rises as the nightmarish Cherubimon, who is able to make the Digimon de-digivolve to their Rookie forms. The group try to fight him as they are but are defeated. T.K. and Kari arrive with their digivolved partners, now Angemon and Angewomon, who are able to put up a decent fight against Cherubimon until he covers the whole area in darkness.All the children suddenly start getting younger, revealing Kokomon is reversing time, and only Veemon, Terriermon, Angemon and Angewomon are spared. Willis realises Kokomons words meant go back in time to when the virus first attacked him four years ago. Angemon and Angewomon decide to digivolve to their Mega-level forms to unlock the Golden Digieggs, which will allow Veemon and Terriermon to digivolve. The two become Seraphimon and Magnadramon, but are quickly defeated by Cherubimon, reverting them back to Patamon and Gatomon. However, their presence summons the Golden Digieggs, Veemon and Terriermon using them to digivolve into Magnamon and Rapidmon.
They battle Cherubimon who launches a sneak attack on them, and devours them. Inside Cherubimons body, they find Kokomons soul who implies they must destroy him from the inside out to eliminate the virus. The two fire their attacks and delete the virus, allowing Cherubimon to turn good, but the damage causes him to be deleted as well, though Veemon and Terriermon survive.
The Digidestined return to New York, where Davis informs Willis that Digimon never really die but rather their data is rebooted and they are born again. Willis parts ways with the other, cheekily kissing Kari and Yolei on the way out, much to Davis fury. He and Terriermon return to Colorado, where Willis calls his mother. Terriermon senses a Digiegg, and Kokomons egg washes up nearby. Kari closes the film, explaining that friendships last forever and Digimon will come back, even if they are singing a different tune. Kokomon, now Wendigomon again, sings rather badly to Smash Mouths Allstar, while Willis watches on in amusement, commenting that his friend is tone deaf.