Gekijouban Pocket Monsters: Koko
A strict rule has been imposed in the deep jungle of Okoya Forest where Zarude dwells. One day, Zarude discovers a human baby and names it Koko, deciding to adopt it in violation of the rule. When Koko turns ten he encounters Satoshi and Pikachu which makes him start questioning who he is. But then one day, the sound of unwelcome human footsteps draw closer to the forest.