Calumon is being attacked by a digimon and somehow appears in the real world. Meanwhile, a boy named Takato finds a mysterious blue card. His obsession with the Digimon game leads him to create a digimon, and when he finds a Digivice the Digivice copies his created digimon's data and creates a real digi-egg. He has a strange dream involving a Digimon Tamer (who is Rika), and his digi-egg hatches. He finds his created digimon, Guilmon, and fears getting attacked by him.

Takato secretly sneaks Guilmon into his house and, in the meantime, Rika, a digimon tamer, and her digimon, Renamon, easily defeat a Goblimon. Takato leaves Guilmon alone while he goes to school, but Guilmon follows him and causes chaos in the school. Takato meets Henry and his digimon Terriermon and thinks he isn't worthy of having Guilmon. While looking for a place for Guilmon to stay, Takato and Guilmon are attacked by Renamon and Rika.

Henry and Terriermon stop the fight between Guilmon and Renamon, and Takato finds a perfect hiding place for Guilmon while he’s away. Guilmon and Renamon resume their fight, and Terriermon gets in the way of an attack. He digivolves into Gargomon but can’t control his powers and almost hurts Rika but she is saved by Guilmon.