On a certain day, before a fight that Masaru had been training for, a strange dinosaur-like creature appears.

On a certain day, before a fight that Masaru had been training for, a strange dinosaur-like creature appears. This strange creature, "Agumon", is a "Digital Monster" from another world, the "Digital World". Masaru and Agumon agree to communicate by fighting. However, Agumon had escaped from and was being chased by an organization which investigates digital phenomena, called "DATS (pronounced 'dats')". DATS attempts to recover Agumon from Masaru. As Masaru and Agumon are chased, they run into the Adult stage Digimon, Cockatrimon. Seeing its enormous form ignites Masaru's combative heart, and he challenges Cockatrimon to a fight. Upon striking Cockatrimon, a "Digisoul" forms in Masaru's fist. When Agumon receives Masaru's Digisoul, he evolves into Geo Greymon and defeats Cockatrimon. Commander Satsuma of DATS, after reviewing the events around Agumon and Masaru, formally appoints them as scouts for DATS. Thus, the captain of the school's fight club, Daimon Masaru, and his partner Agumon, join the fight against the Digimon which are threatening the world's borders.—arorashadow_2003