After disappearing from the underworld, the legendary yakuza known as the "Immortal Dragon" resurfaces — as a fiercely devoted stay-at-home husband.
One day Doraemon, Nobita, Shizuka, Gian and Suneo were shooting a film as space heroes. When they were shooting the film in the open lot a boy called Aron comes and alerts them of aliens attacking his planet. They agree to help him by turning into real superheroes, but it isn't as easy as it looks.
When Nobita goes diving with Doraemon, a mermaid named Sophia comes close to him and they all befriend her. When they proceed towards her kingdom, they encounter a fight between two opposing tribes.
