The story retells the story of the 1999 anime series, in which seven children; Tai (Taichi), Matt (Yamato), Sora, Izzy (Koushiro), Mimi, Joe and T.K. (Takeru), are mysteriously transported to the Digital World, where they meet monster companions known as Digimon. Also including the 8th child Hikari (Kari) later on. Using the power of the Digivice to evolve their Digimon partners into more powerful forms, Tai, his friends and their Digimon companions must work together in order to save both the Digital World and their own. The game also features the story of the film,"Our War Game!", as well as original scenarios exclusive to this game.
Initially, only seven characters and their Digimon partners are available. During the third arc, the eighth character, Hikari, becomes available. During the course of one episode, one character assumes the role of team leader and two other characters' Digimon partners join in battle. Occasionally, the team leader will be able to talk to the other characters mid-episode. By choosing the right answer, the relationship level between those two characters is increased. This has multiple benefits, like an assist attack in-battle and unlocking extra episodes after the main story.
A battle is between a maximum of six Digimon, three on each side. By default, the player controls the Digimon of the team leader and can take manual control of the other partner Digimon through the strategy menu. It has a turn-based system wherein each Digimon can use a regular attack, use special attacks, use items, guard against an attack, or attempt to run from a wild battle.
After completing a main episode unlocking the evolution, the Digimon can digivolve in-battle into their Champion, Ultimate or Mega forms. This significantly increases stats. Evolution consumes special points (SP) and doesn't use up a turn. Post-battle, the Digimon revert to their Rookie forms. Occasionally (for example during the first time a Digimon evolves mid-story), they evolve pre-battle. The evolution sequences from the anime were completely reanimated for this game, unlike the opening theme song which was only cropped to fit the 16×9 aspect ratio of a PSP screen. These sequences are only shown once during the initial evolution, but can be viewed anytime from the library.