Somewhere in the universe lies Planet H12 (pronounced "H-One-Two"). This planet, 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. Named “Teo”, 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 peace is disrupted by a crisis where the same space kaiju who destroyed his home planet suddenly appears on Earth.

When his strong desire to protect overcomes the fear in his heart, a brilliant light transforms Ibuki into a blue giant of light!