The story begins with the emergence of Alien Baltan trying to Earth, but the effort was stymied by a battle Ultraman Cosmos so sweeping outside the earth. Baltan able to discredit the power of the Cosmos and the two entered the Earth's atmosphere and the battle continues. Their arrival as a foreign body was found by the SRC. Meanwhile, elsewhere, a 12-year-old boy named Haruno Musashi and his friends were camping for the summer holidays. But the heavy rain whichfell suddenly made them split up and Musashi left alone in the forest. In the morning, Musashi awakened a strange sound that made him curious. He was seeking the source of the sound, and the voice was coming from Ultraman Cosmos who was dying from fighting the Baltan. Musashi was able to communicate with the Cosmos and he wanted to help restore power. After receiving enough light, and invites Cosmos thank Musashi fly in his hand. After the fall, Cosmos provides a rock and ordered Musashi to save it. Musashi was very pleased and told his experience to parents and friends. But no one believed.
when Musashi 19-year-old . He joins a wing of SRC known as Team EYES. Musashi encounters Cosmos again, and the two merge to defend the Earth.
Cosmos is another type-changing Ultraman, with the all-blue Luna and asymmetrical red and blue Corona modes. The modes represent a "gentle" side and a "strong" side, respectively. Later in the series, Cosmos also develops the "courageous" Eclipse mode, with a symmetrical blue, red, and gold design.