While in the middle of training with Toripter, Hiroto finds a mysterious egg lodged in the Engine's hull and as Toripter tries to lays on the egg to have a little brother of his own. After his Engine is forced to leave his Engine Cast, Hiroto looks after the egg until it hatches, revealing a tadpole-like creature that imprints on Hiroto. He soon learns that he must take care of the creature and keep it happy, as it can produce high-frequency crying that can destroy the city if it is not happy. But Hiroto takes the baby to the Ginjiro-go and there Jum-bowhale reveals to the Go-ongers that baby is a Wameikle from the Braneworld known as Stormy World. Wondering how it got to their dimension, Renn remembers he and Sosuke saw some Ugatz gathering tadpoles and realizes the Gaiark are behind it as an annoyed Miu arrives to demand to know Hiroto's whereabouts. But when the Go-ongers and Miu pound on the Ginjiro-go to talk to him, Wameikle freaks out and hops off with Hiroto in pursuit as the tadpole is captured by the Ugatz, with Hiroto unable to save the baby as Go-on Gold scares it. Hiroto feels bad about not saving Wameikle, with he others offering to fight in his place to save the baby. Things get worse when the Ugatz use their power to forcibly grow Wameikle into its adult form and placed it in a fit of rage to attack the Go-ongers and use its high-frequency screams to break the dimensional barriers so the Stormy World's tornadoes can devastate the Human World. While GunBir-Oh and Kyorestu-Oh deal with the endless tornado onslaught, a furious Hiroto takes down the Ugatz single-handedly before seeing he has no choice but to fight Wameikle. With the new weapon Renn developed, Hiroto manages to calm Wameikle down with its favorite vegie juice as the Engine Combinations restore the Dimensional Barrier. Hiroto then says goodbye to his "child" as Wameikle returns to the Stormy World, with the Go-ongers provoking Hiroto into chasing them after they call him the team's "father figure".