At the shopping district raffle, Dad won a trip to Hawaii! The Panpaka family is thrilled for their first overseas trip. However, Panpaka-kun gets separated from his parents at the airport, boards the wrong plane, and ends up lost in the Banana Kingdom, surrounded by jungle. Mistaken by the king for the "Legendary Underwear Hero," Panpaka-kun finds himself embarking on a journey with Wanpoko the dog, Oson the pheasant, and Terry the monkey to defeat the villain Banana-Wani, who stole the kingdom's treasure. Can Panpaka-kun save the Banana Kingdom from crisis and reunite with his family?