Koromon

Koromon is the In-Training form of Agumon.

Digimon Adventure
Koromon became the Digimon Partner of Tai and permanently Digivolved to Agumon to fight Kuwagamon. He later appeared after Greymon had become SkullGreymon, then when he digivolved to MetalGreymon for the first time fighting Etemon, and again in the fighting with ShogunGekomon, then when WarGreymon and MetalGarurumon defeated Myotismon they returned to Koromon and Tsunomon. WarGreymon also reverted to Koromon after he defeated Machinedramon.

Digimon Frontier
A Koromon was seen at the Autumn Leaf Fair. Another one was at the Village of New Beginnings run by Swanmon.