A mad scientist decides octopuses deserve to rule humanity, so he kidnaps an idol singer who happens to be your secret superhero partner, except you don't know that yet. Perman has to fight a giant octopus while also protecting the girl he likes without realizing she's been saving his life the whole time. The movie finds its comedy in the gap between what each character thinks is happening and what's actually happening, turning a B-movie premise into something that lands harder because the emotional stakes are personal, not planetary.

Dr. Octo, a researcher devoted to octopuses, decides that the eight-legged creatures would make better masters of the planet than humans and sets out to conquer the world. As part of his plan he seizes Sumire Hoshino, a popular idol singer who is secretly Perman #3. Her teammate Mitsuo Suwa, Perman #1, adores the idol without realizing she is his own partner. Furious at her capture, he transforms and rushes off to save her, only to learn that battling a giant octopus is much harder than it seems. The film is a comic superhero adventure, and it was screened at the same time as the 25th Doraemon movie and Doraemon Anniversary 25.