Deep within the Forest of Okoya, the Mythical Pokémon Zarude live in a troop and maintain a strict rule that forbids outsiders from entering their territory. Elsewhere in the jungle lives Koko, a human boy raised by a lone Zarude who left the troop. Koko has grown up never doubting that he is a Zarude. But one day, a chance meeting with Ash and Pikachu leaves Koko with his first human friend. Is he truly a Pokémon? Or is he, in fact, a human? When danger threatens the jungle, the bonds between Pokémon and human-and the love between parent and child-will be put to the test.