Riko's pendant transformed into a mysterious Pokémon. Seeking its true identity, Riko and her friends head to her grandmother Diana's house, where they finally reunite with her in a hidden ancient castle. Diana recounts Lucius's adventures and the mysterious Pokémon "Terrapagos." Meanwhile, the Explorers, led by Amegio, who had been pursuing Riko and her friends, are approaching the castle…

Rico's grandmother, Diana, also joins them on the airship, and the Rising Volteckers soar through the skies once again. For Terrapagos, who has been dormant for many years, the airship is full of things he has never seen before. Rico is constantly being dragged around by Terrapagos, who is adventuring everywhere on his own, causing him a lot of chaos. Meanwhile, Nyaoha seems displeased that Rico is only paying attention to Terrapagos...