Note: This movie was eventually adapted into the second part of the dub's Digimon: The Movie ("Four Years Later"), and many parts of the movie were cut out in order to accommodate for three movies being cut and repasted into one.
The movie is directed by Mamoru Hosoda and is notable for having a very similar plot to his later work, Summer Wars, right down to the core plot, story beats, and even artistic direction. As such, many fans consider Our War Game to effectively be a prototype to Summer Wars.
One night in Odaiba, the lights and electronics go crazy as an egg descends on them...
In the morning, Taichi writes an email to Sora apologizing for some incident that had recently happened and asks her not to be angry anymore. Taichi is so unnerved that he accidentally spells his name wrong at firstnote . Hikari barges in, startling Taichi and causing him to accidentally add a Heart Symbol after itnote , but before he can change it he's too distracted by Hikari showing him the present she's going to give to a friend for her birthday. Feeling a little trollish, Taichi plays at trying to steal the present, but Hikari returns the favor by sending Taichi's email — complete with heart symbol — before he can even react. As Hikari leaves the house, Taichi's computer tells him that his mail has been rejected, and Taichi complains that Sora doesn't want to receive emails from him before collapsing in anger.
While Koushirou's working at his computer, his lines of code begin to go crazy, and as he looks further into it, on his screen — and on the screens of confused children all over the world — a DigiEgg appears.
Taichi is interrupted by Koushirou appearing at the door, ranting that a Digimon egg has hatched. Koushirou enters the house and shows Taichi a jellyfish-like Digimon (Kuramon), who's left a message saying "hello!!". Koushirou explains that the egg was made up of a ton of computer bugs' fragments, having retrieved the information from an American friend who had analyzed the egg shellnote .
The jellyfish-like Digimon evolves and leaves another message: "I'm hungry". Koushirou says that the Digimon eats data to grow, and, while it's only in its baby form now, it could quickly start growing and begin to eat data from all over the network and cause computers all over the world to go haywire. As they speak, the computers all over the world indeed begin to act strangely, with cash registers and printed store labels listing abnormally large prices for various products.
While Taichi and Koushirou rush over to use Taichi's father's computer, Taichi's mother offers them oolong tea, which Koushirou drinks a full cup of. Taichi's father's computer is connected to the internet via an ISDN, and when they load it up they find that the Digimon has evolved yet again, this time into its Child form Keramon. They know that they have to defeat the Digimon soon but don't know how to do it, and Taichi laments that he wishes Agumon were there... only for Agumon, Gennai, and the other Chosen Children's Digimon to appear on the computer.
The Digimon tell Taichi that they'll enter the Internet in order to fight off the new hostile Digimon, saying that it's their turn to save the children the same way they children saved their Digital World. Gennai sends the Digimon to the net while Taichi and Koushirou ready their Digivices, and Taichi goes off to let everyone know.
Unfortunately, Taichi has problems with that part: Jou is off taking exams to get into middle school, Yamato and Takeru are off all the way in Shimane visiting their half-senile grandmother who hangs up on him, Mimi's entire family is out, Hikari refuses to leave her friend's party until the candles have been blown out, and Taichi refuses to call Sora for some reason, telling Koushirou to do it instead. Koushirou, unfortunately, doesn't have any luck; Sora's mother picks up the phone, and, when she tells Sora that the call's from the Yagami residence, Sora refuses to talk. Koushirou immediately picks up that something's off and asks Taichi if somethings happened, but Taichi avoids the subject.
Sora checks her email and receives nothing. Angered, she slams her laptop shut, clutches a hairclip, and declares Taichi to be an idiot.
When Taichi and Koushirou return to the computer, they find that Agumon and Tentomon have been successfully transferred to the Internet. As the two of them enter, they find the Digimon eating up data and attack him with a preemptive strike. The Digimon leaves another message — "Let's play" — and Agumon and Tentomon evolve to Greymon and Kabuterimon, watched by children all over the world on their laptops.
The Digimon evolves again (Infermon), and Koushirou tells them not to worry since he's only an Adult form Digimon, like Greymon and Kabuterimon. However, as the Digimon proves to be much stronger than one would expect from an Adult-level Digimon, Koushirou realizes that the Digimon evolved not once but twice, and is a Perfect-level. Now knowing that he's much more of a threat, Agumon and Kabuterimon super-evolve to MetalGreymon and AtlurKabuterimon... except that the Digimon manages to violate the rule of Transformation Is a Free Action and attacks them mid-evolution, reverting them to their Child forms and escaping. As Taichi and Koushirou let Agumon and Tentomon get some rest, Koushirou gets some emails from children of different countries commenting on the battle, and Taichi and Koushirou realize that their actions are being watched all over the world.
They then find another email, this time from the Digimon: "hellohellohellohellohellohellohello..." Koushirou sees the email address that it was sent from and realizes that the Digimon is in the NTT system. Desperate, Taichi tries to call Hikari again, but she still won't leave her party because she's winning a game of Old Maid. He's unable to call anyone else after that, because every attempt he makes results in a busy signal. One of the calls he makes results in a text-to-speech reading out the Digimons emailnote , and Taichi realizes that the situation's getting progressively more problematic as the Digimon hacks the phone switches and repeatedly calls all the phone numbers in the world in an attempt to bring the system down. With the phone lines down the Internet connection cuts off, and Taichi and Koushirou find themselves in an even more desperate situation.
Koushirou runs out of the Yagami residence in search of a solution, and Yamato, who heard from his grandmother that Taichi called, has a hard time reaching Taichi when the phone lines are busy. Fortunately, the news reports on an emergency voice mail system that people can use to connect to each other immediately, and Taichi realizes that he can use it to contact the others. Taichi sends messages to all of the other Chosen, including Sora, asking for help; Sora finds herself walking all the way over to the Yagami residence and almost opens the door before deciding not to and leaves, once again calling Taichi an idiot. As if things couldn't get any worse, Taichi's mother gives Taichi a postcard from Mimi, who's on vacation with her family in Hawaii.
Koushirou returns with a military cell phone, meaning that they can connect to the internet without an NTT switch. Taichi checks the emergency voice mail box only to find that Yamato has successfully gotten their message, and wants to know what's going on. Taichi and Koushirou leave messages back and forth with Yamato and catch him and Takeru up on the situation, but while Takeru and Yamato have their Digivices, they're not sure if they can find a computer somewhere in Shimane. With not much other choice, Yamato and Takeru leave their grandmother's house and search around for anyone who has a computer.
When Taichi and Koushirou successfully re-connect to the Internet, they find that the Digimon has somehow made it all the way over to America. Fortunately, they're contacted by Yamato and Takeru, who've found a computer in a small barber's shop. As Koushirou slurps down oolong tea, Gabumon and Patamon join Agumon and Tentomon in going off to fight the Digimon, and Yamato and Taichi have Gabumon and Agumon warp evolve to MetalGarurumon and WarGreymon as the children all over the world continue to watch.
Takeru tries to get Patamon to evolve as well, but before he can do so the Digimon evolves to his Ultimate form (Diablomonnote ) and takes Patamon out. Angered, Yamato and Taichi have MetalGarurumon and WarGreymon attack all-out while Tentomon takes Patamon to safety, but the Digimon is too fast for the two Ultimate-level Digimon to leave a mark on him. Koushirou ends up having drunk a little too much oolong tea and leaves for the bathroom, and while Koushirou's out Taichi ends up smacking the computer while watching the battle, causing it to bluescreen. Taichi, no longer connected to the Internet, is unable to hear Yamato yelling that WarGreymon's stopped moving.
Koushirou returns and begins to fix the computer, yelling at Taichi for having frozen it, and when Taichi responds that he didn't do it on purpose Koushirou retorts that this is why Taichi and Sora get into fights. The remark hits Taichi hard, and he finally tells Koushirou what happened: he'd bought Sora a hairclip for her birthday, and they'd gotten in a petty fight over Sora accusing him of not liking her hat.
When Koushirou and Taichi re-connect to the Internet, they find the battleground all torn up and WarGreymon and MetalGarurumon unconscious. The mysterious Digimon holds up a clock and sends a message: "Who has the clock?" The Digimon then begins to clone himself into multiple copies and a timer appears on the screen with ten minutes, ticking downwards towards zero. Koushirou adds some horrible news to the mix: a friend in Taiwan who'd hacked into the Pentagon had found that a military base in America has sent a missile due to a "bug" in the launch system. Taichi and Koushirou realize that the Digimon is responsible for this, and that the clock is a countdown to when the missile hits — and, since the missile is powerful and fast enough to hit anywhere in the world, they can't stop it in the air.
Koushirou receives more emails from children around the world, this time begging them to defeat the "monster". Since the military missile will only explode if the fuse activates, Koushirou says that if they can defeat the Digimon that has the clock and not just one of its duplicates, the fuse won't activate and the missile won't explode. Taichi protests that it'll take too long to find the real one, but Koushirou says that it's the only way, and WarGreymon and MetalGarurumon, despite being injured, decide to take on the challenge. With seven minutes left and emails of support coming in one by one, the two of them chase after the Digimon.
They arrive to an area swarming with copies of the Digimon, with the number duplicating every second. With all of the copies constantly duplicating and attacking at once, and with all of the emails of support from the children all over the world slowing down WarGreymon and MetalGarurumon, the two of them are quickly incapacitated. In desperation, Taichi reaches towards the screen and finds himself going right through it and into the Internet space. He reaches for WarGreymon as Yamato likewise enters and reaches for MetalGarurumon. Taichi yells to WarGreymon, saying that hes here and won't let WarGreymon fight alone. Taichi's words and the emails from the spectators surrounding them cause WarGreymon and MetalGarurumon to regain strength, and the power of the emotions coming through all of the emails allows them to combine into Omegamonnote .
Omegamon is capable of releasing a rapid-fire series of attacks at all of the copies of the Digimon, successfully reducing them to only one: the real one, who has the clock. Omegamon, with Taichi and Yamato on his shoulders, chases the Digimon, but it proves to be far too fast for him. The situation becomes desperate as the missile approaches Odaiba...
At thirty seconds left, Koushirou gets the idea to forward all of the emails the international children are sending him to the Digimon in the hopes of slowing him down. With the press of a button, the Digimon is immobilized by lag, and Omegamon manages to stab the Digimon — and the clock — at the exact moment the clock hits one second.
The missile lands without exploding in the waters near Odaiba. While Taichi and Koushirou stare at the scene in exhaustion, Sora checks her email to find the email from Taichi (with the heart symbol), and as the wave from the giant splash the missile's made washes up in the background, she cheerfully proclaims Taichi to be an idiot.
Over the credits, we see the short-term aftermath of the incident: Takeru smiles happily with a couple he met at the barber's shop, Yamato is subjected to a haircut at said barber's shop, Jou finishes his middle school entrance exam in exhaustion, Mimi returns from America with a ridiculous tan, Hikari enjoys the rest of her friend's birthday party, Koushirou departs from the Yagami house, and the Chosen's Digimon and Gennai smile happily at them from the computer. Finally, Sora sends an email apologizing to Taichi and thanking him for the present... and we see a picture of her wearing the hairclip that he gave her.
- Chekhov's Gunman: See that girl in a bandanna typing emails? That's Miyako Inoue, one of the Chosen in Adventure 02, and this is the event that would make her into a Chosen Child.
- Combat Pragmatist: Keramon skips the Champion level, digivolving straight into Infermon, his Ultimate form. When Greymon and Kabuterimon try to match it, he attacks them while they're still digivolving and immobilized.
- Computer = Monitor: Somehow, Taichi smacking the monitor causes Windows to BSoD.
- Evil Sounds Deep: Diablomon has a very deep voice in the dub.
- Expy: Diablomon is one of Millenniummon: Both have disproportionate strength for their levels and some kind of connection to time. Even their body-structures are similar; Millenniumon's lower set of arms, and legs is largely identical to Diablomon's, and both have armored heads, with wild hair. Given how much else he's done, Millenniumon may well have originally caused the viral egg, and influenced it to develop in his own image.
- Funny Background Event: When Agumon and Tentomon are preparing to transfer themselves to the Internet, Tailmon can be seen walking into a wall.
- One Steve Limit: The girl having a birthday party in the movie is named Noriko, whos not to be confused with a minor character who has a semi-significant role in the later episodes of Adventure 02.
- The Operators Must Be Crazy: The dubbed version has the operator get progressively more and more irritated at Tai as he continues trying to call everyone. The original just has the beep of a busy signal.Operator: Didn't you hear me?
Tai: But I thought...
Operator: IT'S BUSY!
Tai: (meekly) I'm sorry, lady...
- Painting the Fourth Wall:
- The digivolving transformation sequences are seen, as the show's audience normally sees them, in-universe on everyone's computer screens.
- "Brave Heart," the song that always plays during the show's fight scenes, stops abruptly when Diablomon attacks Patamon, and resumes when MetalGarurumon attacks in retaliation. When the scene goes back to Taichi and Koushirou watching from their computers, the song is softer with more static, like it's coming out of the computer's speakers. When Koushirou's Potty Emergency kicks in and the computer starts lagging, the song starts skipping and getting stuck on the "Show me your brave heart" line over and over again, until it cuts out entirely when the computer crashes.
- Pre Ass Kicking One Liner: Courtesy of the dub, we get Izzys awesome line as he hits the button to forward all of the emails to Diaboromon: "You've... got... mail!"
- The original has the slightly less awesome but still pretty impressive "Go...!"
- Ship Tease:
- According to Mimi's voice actress Ai Maeda, the incident between Taichi and Sora was what got her to ship them.
- In the dub, we get a cute one between Mimi and Joe where Joe has apparently left a Valentine or something like that in Mimi's mailbox. In the Japanese version, it was just Mimi's family's nameplate.
- Transformation Is a Free Action: Subverted for the first time in the series — Infermon attacks Greymon and Kabuterimon right in the middle of their transformation into MetalGreymon and MegaKabuterimon, knocking them back to being Agumon and Tentomon and raising some questions about how the whole process works to begin with.