Tai and Koromon are pulled through the rift and find themselves back on Earth. Tai goes home and visits his little sister, Kari, who seems to be aware of the DigiWorld. He also discovers that evil Digimon are taking advantage of the rift and creating chaos on Earth. Koromon digivolves to Agumon in order to battle the dreaded Ogremon and then returns to the DigiWorld to help his friends. Although Tai wishes he could stay with Kari, he follows Agumon back, too.
Tai and Agumon return to the DigiWorld, where they look for their friends. They find Tokomon, who tells them that the other kids split up to look for them. He and T.K. met up with a new Digimon, Demidevimon, who seemed to be a friend but caused the two to have an angry fight and go their separate ways. Tai, Agumon and Tokomon find T.K. and Demidevimon, and Tai tries to get T.K. and Tokomon to make up. Demidevimon senses he's losing his influence over T.K. and tries to get the others to eat some mushrooms of forgetfulness, but they're warned off by a mysterious female voice (Sora). Realizing that Demidevimon isn't a true friend, Tokomon digivolves to Patamon and drives him off.
Matt and Gabumon find Joe slaving away in the kitchen of Vegiemon to pay for his meal. But a series of mishaps keeps Joe even deeper in debt. Joe doesn't know that DemiDevimon has ordered Vegiemon to keep Joe working there forever! Just in time, Tai and T.K. arrive and reveal DemiDevimon as an evil Digimon. A battle ensues, with Joe sacrificing himself to save T.K. as Gabumon digivolves first to Garurumon, then to WereGarurumon. The evil Digimons are defeated as the boys resume their search for Mimi and the others.
Searching for Gennai, Izzy and Tentomon find themselves trapped and suddenly fall beneath the surface into a bottomless pit. Vademon tricks Izzy into giving up his curiosity and his worldly possessions and brings Izzy's Tag and Crest to DemiDevimon. Tentomon feels that he is losing Izzy and de-digivolves into Motimon, who helps Izzy retrieve his Tag and Crest as well as his curiosity, then Motimon digivolves to MegaKabuterimon, who defeats Vademon. Izzy and Tentomon are thrust back to the surface where they find Matt, T.K., Tsumonon and Patamon.
Tai, Joe and their Digimon companions track Mimi to a gigantic fortress where she's being treated like a princess by frog-like beings called Gekomon. The Gekomon are convinced that only Mimi's singing can awaken their master, ShogunGekomon. Mimi strings them along, never quite awakening the sleeping giant. When Tai and Joe call her a spoiled brat she has them all thrown into a dungeon. Finally, in a nightmare, Mimi sees what she's become. She begs everyone's forgiveness and awakens ShogunGekomon, a destructive behemoth who was better left in a coma. It takes an appearance by Metal Greymon to put the brute back to sleep.
The reunited children find a very emotional Sora, who explains that DemiDevimon told her that her Crest of Love would never glow because she never had love in her life. When DemiDevimon sees all the children together, he and Myotismon attack. However, since Sora realizes her mother did love her, and was only trying to protect her, her Crest begins to glow. Birdramon digivolves to Garudamon and defeats Myotismon. But before the children get too comfortable, the voice of Myotismon tells them they are about to meet their doom!
Gennai tells the kids about an eighth "digidestined" child, who is currently living in Japan. Planning the capture of that child, Myotismon has discovered a gate in the castle that will allow him to pass into the human world. Demidevimon pulls together some troops, as the kids manage to search the castle for the gate. When the troops appear the Digimon digivolve and scare them away before they are able to get through the gate. A ferocious Digimon named Devidramon attacks and Greymon digivolves into Metal Greymon and destroys Devidramon. Gatomon closes the gate before the kids can get through it.
The gang watches helplessly as Myotismon slips through the gate into the real world to find the eighth child. At Gennai's house under the lake, the wise old man gives the kids ten Digimon key cards, which, if played correctly, will open the gate. Before they can be used, however, the kids must learn the key cards' secret. Back at Myotismon's castle, the kids' Digimon battle Dokugumon, the castle's spider guardian and his parasite minions. At the last second, Izzy cracks the code of the cards and the kids leap through the gate!
The kids are back in the real world at camp and must stop Myotismon before he finds the eighth child. They go to Highton View Terrace, where they are attacked by Myotismon's army. The kids suddenly realize that what they though was a bombing attack four years ago, was actually the appearance of the first Digimon. Izzy suggests that the eighth child must have been there, as well. The kids continue to search for the child before Myostismon can find him or her.
Trying to get home, the kids take the subway with the Digimon pretending to be stuffed animals. They sleep through their stop and end up somewhere in the city. Luckily, they are spotted by Sora's cousin Duane, who picks them up. Duane accidentally knocks Izzy off a bridge during a confrontation and Motimon digivolves into Tentomon and saves him. Demidevimon and his henchmen appear. The Digimon digivolve and the kids are saved.