A cheerful entrepreneur named Mr. Sunshine has arrived on a vibrant island world with an enticing offer: local inhabitants can receive easy money by collecting scrap for his colossal robots. Meanwhile, a small red creature called Piku awakens in a cave after being roused by a mysterious ghost, only to emerge into a world where legend has cast him as a dangerous villain. Distrusted and confined by the island's inhabitants, Piku slowly rebuilds his reputation through good deeds, including repairing a bridge he inadvertently damaged. As he gains acceptance and ventures deeper into the island's secrets, Piku uncovers the sinister truth behind Mr. Sunshine's operation—his machines are systematically draining the island's vital resources. Compelled by this discovery, Piku allies himself with a group of resistance fighters working to thwart the exploitation and save their home.