After the tower that holds all of the digitalized humans turns into Quartzmon, Ewan Amano realizes that the Hunters are protected by their Fusion Loaders. Quartzmon gets ready for a second attack, creating a Myotismon, which prompts the others to flee. The hunters gather at a small island that is protected by Clockmon, where the hunters and the Old Clock Shop Man are waiting. The Old Clock Shop Man asks Mikey Kudō if he remembers the island, which he replies that it was the place that he fought Lord Bagra a year ago. The Old Clock Shop Man explains that that fight had brought Quartzmon into existence, as well as leaving behind the last of Lord Bagra's powers behind, which would become a weapon to hunt Quartzmon with.
The Old Clock Shop Man explains that Quartzmon is a distortion of the human world's expanding digital power that came alive during the fight with Bagramon. Quartzmon had changed into particles that expanded DigiQuartz across the globe, which became a limit to the number of Digimon that could be out at one time. Quartzmon then brought Digimon from the Digital World to steal their data and gain more power, most of which had gathered in Japan because Bagramon's fight had occurred there. This was countered by a plan of the Old Clock Shop Man, who had enlisted several children to Hunt the Digimon before Quartzmon could steal their data as well as dealing with any other lost Digimon that would have ended up overseas. However, more people were required to deal with this problem, so the Old Clock Shop Man had brought others from the dimensions of Digimon Adventure, Digimon Tamers, Digimon Frontier, and Digimon Data Squad to help. This included Taichi "Tai" Kamiya and Marcus Damon, who were the heroes of their respective dimensions. The Old Clock Shop Man explained why he didn't want Mikey to join the Hunt; that it would throw off the balance because Mikey was the hero of this dimension, and that the Hunt was also a way of training people to use the weapon made from Bagramon's power along with the help of the six heroes, the one to use the weapon being the best hero.
Quartzmon draws closer, so Mikey, Christopher Aonuma, Nene Amano, Ewan, Angie Hinomoto, and Jeremy Tsurugi are asked to deal with Quartzmon and the copied Myotismon, Angie and Jeremy getting an orange and teal Fusion Loader respectively, symbolizing the courage and friendship they used to help Shoutmon digivolve into OmniShoutmon. Angie is given Cutemon and Dorulumon while Jeremy is given Ballistamon, and the six members of the Fusion Fighters United Army head off. Before they fight, Shoutmon notices that Beelzemon was inside Nene's Fusion Loader, but Mikey says it doesn't matter since they are all a part of Xros Heart. Ewan uses DigiFuse on Tuwarmon and SuperStarmon, Nene digifuses Mervamon and Beelzemon, Jeremy digifuses Ballistamon and Deputymon, Angie digifuses Dorulumon and PawnChessmons, while Mikey and Christopher digivolve Shoutmon and MetalGreymon, then perform a Double Fusion with the two.
Meanwhile, Clockmon has sent the remaining Hunters into an image space where they can decide who is the best and use the Brave Snatcher. Tagiru Akashi and Gumdramon volunteer as well as Ren Tobari and a few others, but Ryoma Mogami proclaims that he cannot hand the honor to anyone else. Therefore, Astamon and Arresterdramon are to fight to determine who is the best Hunter.
At the town, Xros Heart has managed to defeat most of the Myotismon, but Quartzmon creates MaloMyotismon and VenomMyotismon, which defeat their Digimon. Mikey tells Shoutmon to stand up, who in turn responds that he has to fight for the sake of his juniors. A voice from above approves what he says, revealed to be Marcus and Agumon Burst Mode, the former punching a VenomMyotismon into two others. The two of them introduce themselves, while Agumon complains that Marcus's Agumon can fly. Tai tells him not to mind this, and they introduce themselves as well. A VenomMyotismon tries to attack them, but Magnamon blocks the attack with his own. Davis Motomiya introduces himself, saying that Tai is his senior, but they are the same age at the moment. The confusion is cleared as Takuya Kanbara elaborates that they are from different times, and introduces himself while noting that though he doesn't have a Digimon with him, he is fine. Takato Matsuki claims how cool it is to see Davis and Tai in action, and introduces himself as a Tamer with Guilmon. Tai says he can't be shown up, and warp-digivolves Agumon while Marcus warp-digivolves his Agumon as well. Takato biomerges with Guilmon while Takuya fusion evolves into Aldamon, who flies up into the sky along with WarGreymon, Gallantmon, and ShineGreymon, as well as Marcus.
Meanwhile near an ancient pyramid, Joe Kido defeats a mini-Quartzmon, then notices that the others are gone. Gomamon tells him that they all left to go to Tokyo except him, leaving Joe shocked. Magnamon degenerates into Veemon, Davis complaining about how Magnamon can only be used for a short time. But Ken Ichijouji and Stingmon show up along with Matt, MetalGarurumon, and Takuya's friends. Kumamon tells Aldamon that he brought all of the Spirits, leading him to digivolve into Susanoomon while Veemon and Stingmon DNA digivolve into Imperialdramon Fighter Mode and WarGreymon fuses with MetalGarurumon to make Omnimon. Jeremy confuses these with DigiFuse, but Tentomon explains each of the Digivolutions. Additionally, Grani returns to Gallantmon to make Gallantmon Crimson Mode and Marcus changes ShineGreymon into ShineGreymon Burst Mode. Along with Marcus and OmniShoutmon, they manage to defeat all of the copied Digimon, but did not harm Quartzmon at all.
In the image space, Astamon has managed to defeat Arresterdramon, making Ryouma the candidate. They return to the island along with the legendary heroes, who help Ryouma drag the Brave Snatcher out of the sea. But Ryouma claims that it is troublesome for all of the heroes to be there, so he attacks Mikey and OmniShoutmon with the Brave Snatcher, injuring them gravely. Ryouma announces that he was an ally of Quartzmon from the start, shocking the rest of them, Quartzmon confirming this. With Mikey injured, the Brave Snatcher is again sealed in the ocean, unable to be used as Quartzmon looms closer.
Featured characters[]
(Numbers indicate order of appearance. Bolded characters are fought by the protagonist(s), and italicized characters feature non-explicitly, e.g. voice, silhouette, image.)
Clockmon: "something" Old Clock Shop Man: "He spreads his cape like a bat's wings to fly!" Tagiru: "DigiXros with Yaki'imon! DigiXros!" Gumdramon: "He can't fly with wings made out of newspaper" Tagiru: "He can if he does it like this!" Gumdramon: "What is he, a paper airplane?!"
MagnaGarurumon and Beetlemon are seen battling at separate areas. This should be impossible, because MagnaGarurumon requires the Spirit of Thunder.
It's possible these scenes were meant to happen at different times.
Animation errors
The MaloMyotismon appearing in front of XrosUpTuwarmon has its skin the same red color as its mask.
"Agumon Burst Mode"'s aura is miscolored as dark purple rather than crimson.
Magnamon's hands are shown having three fingers despite having five in Digimon Adventure 02.
When Takuya fusion evolves into Aldamon, only one ring of Fractal Code is seen on his hand, despite Fusion Evolution requiring multiple rings of Fractal Code in Digimon Frontier.