Passionate athlete Taiki Kudou tries to help a strange creature in need only to be transported with Akari Hinomoto and Zenjirou Tsurugi to a place known as the Digital World. There they meet the strange creature Shoutmon and more creatures who are known as Digimon.
Taiki stands next to Shoutmon, Ballistamon and Dorulumon, leading the Xros Heart army into battle against the Bagra Army. Holding up a red device, a X Loader, Taiki shouts "DigiXros!" In response, the three Digimon become Shoutmon X4 and display immense power with the Star Sword by wiping out waves of the Bagra Army. Greymon jumps out and challenges Shoutmon X4 and, as the two collide Taiki jerks forward, revealing it was just a dream. Meanwhile Akari Hinomoto, Taiki's childhood friend, is looking for him and calls Taiki's mother only to find out he has gone out for a sporting event without her. After being momentarily sidetracked, Akari figures out where Taiki is and rushes off with supplies.
At school Taiki finishes up a basketball game which his team wins thanks to his skills and great teamwork. Akari barely makes it in time to save an exhausted Taiki from hitting the floor. While Akari reprimands Taiki for being so careless, Zenjirou Tsurugi appears, announcing a challenge to his "eternal rival" Taiki who beat him at a kendo match. While Akari and Zenjirou fight, Taiki hears a boy's voice say "I'm going to die." Taiki hurries to find the source of the voice to help while Akari and Zenjirou chase after him.
Electronic things begin to go haywire, the sky flashing colors and showing digital coding. A car appears stuck halfway in a building though neither the car or building is damaged. The voice shouts out a warning and Taiki knocks Akari and Zenjirou out of the way, narrowly avoiding being hit by the car as it falls. Rushing into an alleyway, Taiki discovers a small digital version of a hurt Shoutmon. A light appears revealing a X Loader while a voice asks Taiki if he wants to protect Shoutmon. Saying yes, a light envelops the three kids as Taiki reaches for the X Loader.
Waking up from their fall, Taiki, Zenjirou and Akari find themselves sitting in strange place that is filled with lush green grass. From the X Loader on Taiki's belt they hear Shoutmon's voice. Before they can figure out where they are, they encounter an army of Mammothmon and their leader MadLeomon who attacks them. Ballistamon appears from underground and counter's MadLeomon's attack, saving the bewildered kids. Shoutmon "reloads" out of the X Loader and attacks the enemy with the help of Ballistamon, Starmon and some Pickmon. Taiki uses his X Loader to Digi-Xros Shoutmon and Ballistamon into an incomplete Shoutmon X3. Unable to hold the form, the two change back while MadLeomon absorbs his digimon soldiers.
Once more Taiki uses DigiXros to change the Starmons into the Star Sword. With the Star Sword, Shoutmon defeats MadLeomon, causing him to revert back into his original state and release his absorbed soldiers. Before he can attack again, MadLeomon is forcefully withdrawn with his injured forces by Tactimon, who saw the failure along with Lilithmon, Blastmon, and Baalmon.
Celebrating the victory, Shoutmon informs Taiki that he is a General since he can use Digi-Xros. Shoutmon adds that with the power of Taiki he has a chance to become king of the Digital World. When Taiki and the others remark they don't know what Digimon are, Shoutmon tells them they are in the Digital World, earning a reaction of surprise and disbelief. Nearby, Nene Amano and Kiriha Aonuma observe the group.