Middle schooler Taiki Kudou stumbles into a war-torn Digital World and finds Shoutmon, an underdog Digimon determined to become its king, badly wounded after a battle with the invading Bagra Army. Taiki helps him back on his feet and forms Xros Heart, an army built around DigiXros, a fusion technique that combines Digimon into new, more powerful forms. Friends Akari Hinomoto and Zenjirou Tsurugi are pulled in from his own world. As Xros Heart pushes back against the Bagra Army's hunt for Code Crown fragments, Taiki also crosses paths with rival human generals Nene Amano and Kiriha Aonuma, each building armies of their own.