Gintoki and the others were tossed into the ocean on their way to Ryugu Palace and are now stranded on an unknown deserted island. They search the island for any resources to help survive and are reunited with Kamenashi. Amazingly, the island was Ryugu Palace. Meanwhile, giant turtle robots have appeared in Edo and Gintoki and the others hear about it on the news on TV. According to Kamenashi, Otohime, the owner of Ryugu Palace is carrying out a devious plan.