Le film se focalise sur les origines d'Ultraman qui devient ami avec un petit garçon appelé Musashi. Il est basé sur la série télévisée Ultraman Cosmos et a pour suite Ultraman Cosmos 2: The Blue Planet puis Ultraman Cosmos vs Ultraman Justice: The Final Battle..
Ultraman Cosmos is a Japanese tokusatsu TV show being the 17th show in the Ultra Series. Produced by Tsuburaya Productions, Ultraman Cosmos aired from July 7, 2001 to September 28, 2002, with a total of 65 episodes, which currently makes it the longest running Ultra Show to date. Ultraman Cosmos was also the 35th anniversary for the Ultraman series In June 2002, Cosmos was taken off of television for several weeks when lead actor Taiyou Sugiura was questioned in an assault and extortion case. When the case against Sugiura was dropped for lack of evidence, Cosmos was put back on the air. TBS and Tsuburaya ultimately pulled five episodes from broadcast to make up for time lost, and these episodes were later released on DVD..
Once again, Musashi has encounter Ultraman Cosmos. Now Ultraman Cosmos has gained some new modes to defeat Scropis. Musashi has joined Team Sea to save the Blue Area. But there is mysterious evil monster, Sandros, who wants to destroy the Earth. Now it is up Musashi and Ultraman Cosmos to defeat Sandros and who’s the other Ultraman?.
It has been a year since Musashi retired from being a Team EYES member and now he is finally pursuing his dream of becoming an astronaut..
An alternate version of Ultraman Cosmos 2: The Blue Planet, which was created due to the arrest of the film's star, Taiyo Sugiura. New scenes were filmed that are primarily set in the past. Musashi Haruno, now a middle school student, continues to pursue his dream to become an astronaut, which is also a promise he made with Cosmos. However, he is on the verge of despair because space development gets canceled due to a rocket accident. A mysterious girl named Shau appears in front of Musashi. She invites him to a mysterious parallel space and shows him a vision of what will happen to him 10 years from now. He witnessed a crisis of Earth's destruction caused by Sandros, the worst destroyer in the universe!.
