At the entrance of the forest, "Yukinari" encounters a girl named "Toki." After heeding Toki's warning that "if you hear the voice of the forest, you must not wander around," Yukinari ventures into the woods. Inside the forest, while trying to protect "Celebi" from hunters, Yukinari is swept up by "the power to travel through time" and transported 40 years into the future. In this future world, Yukinari meets Ash and his friends. However, in this era, the strongest man in Team Rocket's history, "Vicious," is plotting to capture Celebi. Armed with Dark Balls that can corrupt any Pokémon, Vicious snatches Celebi away from Ash and the others. To rescue Celebi from Vicious's clutches, Ash and Yukinari fight desperately. But the gentle Celebi has already undergone a drastic change... Amid the intense battle, the legendary Pokémon "Suicune" appears! Can Ash and the others save Celebi and the forest!?