Takuma Momotsuka is a middle school student who attends a historical studies extracurricular activities camp during spring break.

On the second day of camp, Takuma and other camp kids visit a shrine where a festival surrounding the local “Beast Gods” will be held. While exploring the shrine, he encounters a mysterious monster named Koromon.

Immediately following, they hear a scream and find more of their friends being attacked by monsters. Upon realizing he has to save everyone, Koromon evolves into Agumon to fight.

With the help of Agumon, Takuma managed to repel the monsters, but he soon realized that the surrounding area was covered in fog and he had gotten lost in an unknown world…

[Edited from Gematsu's translation]