Having learned that Professor Oak is to be on a nearby island, Ash & Co. decide to stop by to help him with his research. On the island, they learn it is filled with the Pokémon, Rotom, and Professor Oak is on the island to fully research Rotom's special form changes. As they arrive in the area, they soon find three Rotom and try to see what electricity the Rotom enjoy. However, Rotom soon decides to change its form and starts to cause chaos. Will Professor Oak get what he needs, or will Team Rocket stop him from fulfilling his research?

Arriving on Migration Island, Ash & Co. witness a massive amount of Metapod evolve into Butterfree and fly away, as is tradition on the island. However, as the Butterfree leave, Ash notices a wild Caterpie emerge, having not even evolved into Metapod yet. Remembering his own Butterfree, Ash decides to help the Caterpie to evolve so it can leave on time with its family. However, Caterpie struggles with the training due to its love of sleep, but things get even worse when wild Ursaring appear and start causing hassle. Will Ash be able to help the Caterpie?