After his home planet, H12, is destroyed by space kaiju, a lone alien named Teo escapes to Earth and lives as a veterinary student. When the same threat arrives, his will to protect transforms him into a giant hero—Ultraman.
Somewhere in the universe, Planet H12, which closely resembles Earth, is suddenly attacked by space kaiju from another planet. As the planet collapses and faces extinction, one lone alien escapes to Earth. His name is "Teo", a the lonely alien who will eventually grow to become Ultraman. On Earth, he lives as Ibuki Mitsuishi, a third-year veterinary student at Meishin University. Although he struggles with the common sense of Earthlings, he leads a peaceful life communicating with the animals he loves. However, the same space kaiju that destroyed his home planet suddenly appears on Earth, bringing a crisis. When his strong desire to "protect" overcomes the fear in his heart, a brilliant light transforms Ibuki into a blue giant of light!