Princess Darenanda and Arenanda were on their way to Japan on the maiden voyage of the luxury cruise ship Rosebud to deliver Muscle Carrot, a secret elixir that is said to dramatically power up superhumans, to the righteous superhumans. However, a cruel superhuman army targeting the Muscle Carrot appears and takes over the Rosebud. Arenanda escapes alone and asks Mantaro, Kid and the others for help in rescuing the captured princess. Mantaro is the only one who hates scary things and tries to refuse, but when he notices that the princess is exceptionally beautiful, he is motivated! The group infiltrates the Rosebud in a Cessna! Will Mantaro and his friends be able to rescue the kidnapped princess? And what is the purpose of the evil superhumans who are targeting the princess?