Professor Kaneda creates the ultimate soldier robot, Tetsujin, as a substitute for his son, Shotaro, whom he believed died in a bomb raid on Tokyo during World War II. To prevent the army from using Testujin as a tool for destruction, the professor hides it on a remote island. Ten years after the war, Tetsujin is finally resurrected after 28 attempts made by the late Professor Kaneda's protege, Professor Shikishima.

Professor Kaneda creates the ultimate soldier robot, Tetsujin, as a substitute for his son, Shotaro, whom he believed died in a bomb raid on Tokyo during World War II. To prevent the army from using Testujin as a tool for destruction, the professor hides the it on a remote island. Ten years after the war, Tetsujin is finally resurrected after 28 attempts made by the late Professor Kaneda's protege, Professor Shikishima.

The American mafia arrives in Japan with the intention of stealing Tetsujin No. 28. But thanks to Shotaro's quick thinking they are put in their place. Kenji Murasame is willing to help them in their quest but soon discovers that the mafia has it's own agenda. Irritated by all this, Murasame aids Shotaro, but are his intentions entirely pure?

A failed experiment from the war years demonstrates an overwhelming power comparable to Tetsujin's, and Professor Shikishima is taken hostage! Professor Shikishima learns about the ill-fated man's past and a bittersweet story comes to light.

The journey begins with a rumor that a small robot is responsible for the arson of a treasured Kyoto temple. Meanwhile, people involved with a clandestine artificial human project called Robby are murdered one by one, and somehow Professor Shikishima is involved. After a bizarre shoot out a man whispers an ominous phrase "Bagume, Kokurymaru." What is the uniting force fueling all of these conspiracies and tragedies?

The late Professor Kaneda's Sun Bomb is discovered hidden inside of Tetsujin 28! This discovery upsets the entire nation, and a "Tetsujin Inquiry" is set to convene. Meanwhile, the rampage of the PX Syndicate puts Japan at risk of stalling its post war recovery. The only way to stop this mayhem is to boost Tetsujin's destructive capability by injecting the "bagume" into him.

A cyber terrorist bent on revenge attacks Tokyo with a menacing giant robot called the Black Ox. Its power is so great that the entire combined might of the Japanese police is no match for it. Amid the chaos and destruction, elementary school student Shotaro Kaneda (Shosuke Ikematsu) receives a phone call from an elderly man who reveals an astounding secret... his deceased father created Tetsujin 28, a giant robot powerful enough to stop the Black Ox!