Spring break turns into a summer war when the evil Diaboromon wreaks havoc on the internet, and Tai and Matt must achieve a new Digivolution to defeat him! Will Tai and the Digidestined save the world, and will Sora ever forgive Tai for giving her a hair clip?

Six months after the D-Reaper was destroyed, the Tamers are planning to throw Rika a surprise party, but Rika finds out. Suddenly a train-Digimon named Locomon begins to race around the tracks, causing havoc. The Tamers respond to this, as Takato digivolves Guilmon into Growlmon to stop the train Digimon but fails as Takato, Rika and Renamon get on it in an attempt to slow it down. The others, excluding Suzie, use a freight train to catch up with Locomon

Omnimon confronts Mephistomon (who was formed from Apocalymon's data) in a dark corner of the Digital World over Mephistomon's attempt to destroy both the Digital World and the Real World and incorporate the data in order to become truly invincible. They fight, but then Mephistomon sees a chance and slips into the Real World.

The Digital World is becoming so overpopulated that the super computer Yggdrasill who governs the Digital World can no longer handle it. Its solution is Project Ark: to wipe out most of inhabitants with the X Program. Yggdrasill chooses a very small percentage to be moved to a new Digital World and then proceeds to destroy the old one. Some Digimon who were not chosen survive anyway, and they move to the new world with a rare gift known as the X Antibody; this antibody changes their appearance and makes them more powerful, while at the same time making them immune to the X Program. No longer in control, Yggdrasill uses the Royal Knights to destroy these X-Digimon, who are outcasts in the new Digital World.

The Dematerialization Phenomenon, in which the real world becomes digital, has become a problem and must be resolved immediately. After hearing of this incident, Netto and Rockman left off after their father and Network Researcher, Yuuichirou. He also had found news of an invasion in the computer of the Trinity Brain trust company: 'The Earth itself will understand the way things stand in the cyber world'. In order to destroy the program causing the incident, Netto and Rockman have to go deep underground. But old enemies await them there, as well as new ones. As they fought each other, the vicious cyber-life, Nebula Grey, awakens. The Dematerialization Phenomenon will not be stopped unless Nebula Grey is defeated.

After years of inactivity, the DigiDestined regroup with their Digimon to save their world, but have the years changed their characters too much?

After seeing Meicoomon's abrupt transformation and killing of Leomon, Agumon and the other Digimon are kept isolated in Koushiro's office in order to prevent them from infection, but signs of infection begin to appear in Patamon.

The DigiDestined go to a nearby hot springs theme park and everyone has a good time, but Joe doesn't show up because he wants to study for his exams. Another infected Digimon, Ogremon, attacks Odaiba. Gomamon runs away from home while Mimi faces problems with the other DigiDestined and her classmates because of her selfish ideas.

Upon arriving at the Digital World after the "reboot", the Digidestined are hunted by a new villain. Meanwhile, Sora is troubled by her partner Digimon's indifference towards her.

Digimon Adventure 3D: Digimon Grand Prix! was first shown in July 2000 in Sanrio Puroland and in Sanrio's character theme park Haromy Land. The movie was later rerun at Toei's anime festival "Tobidasu! 3D Toei Anime Matsuri" on 03.10.2009. Together with Digimon Savers 3D: Digital World Kiki Ippatsu!, and 2 other CG anime works by Toei, it was released on DVD on 21.02.2010.