A second lieutenant of the Maritime Self-Defense Force, Takafumi Arito (Kenya Ohsumi), who was investigating a UFO that crashed in the Pacific Ocean, encountered a sudden blue light. Under the influence of the light, his genetic genes were distorted and he turned into a vicious monster, THE ONE. After that, he (THE ONE) escaped from the surveillance of the special agency BCST (a research agency for bioengineering) within the Defense Agency and has not been heard from since. On the other hand, Shunichi Maki (Tetsuya Bessho), a pilot of the Air Self-Defense Force F15J, decided to resign from his post in order to spend more time with his son, Tsugumi, who suffers from a congenital disease. During his last flight, Maki met the "red light" in the air. This happened three months after the theone incident. However, Maki miraculously survived and then changed his job to become a civilian pilot and started a new life. There are still agencies that are very concerned about Maki, especially Sara Mizuhara, the chemistry officer of BCST. BCST forcibly took Maki away and physically monitored him in the BCST laboratory built in an abandoned factory. At this time, the missing monster THE ONE seemed to be attracted by something and came back. Maki, who was on the verge of death after being attacked by THE ONE, had his body changed and transformed under the power of the red light ball! Maki, who became a 10-meter-tall steel body with a silver glow and occasionally had his own will, fought against THE ONE, but because the transformation was incomplete, the energy was quickly consumed, and after being hit by a decisive blow, he turned back to the form of Maki Shunichi. Then Sara named this life form that appeared after THE ONE "THENEXT". Maki learned about his son Jimeng's hospitalization on the way back to the BCST laboratory from Tokyo, and met his wife Rongzi again after rushing to the hospital. At this time, the biggest crisis for mankind appeared. "THE ONE", which had mutated after absorbing various creatures into its body, reappeared on the streets of Shinjuku, and the super-flame light bullets emitted from its mouth burned the streets to ashes. The sad personality has been replaced by "THE ONE" and has become unable to turn back into a human. However, there is a sense of sadness. In the past, he and Sara Mizuhara were engaged. For the memory of Sara, for the promise to his son Tsugumi, and to protect his beloved family, Maki transformed again. The figure evolved to a gigantic 40m, with a bloody red color in the middle part, and the characteristic of the elbows is the appearance of elbow blades. Now, with the Shinjuku sub-center as the stage, the fire of the decisive battle between ULTRAMAN and "THEONE" has begun to burn!