Kaizer is the central antagonist of the anime Red Baron, a figure whose true identity is that of Dr. Tetsuo Saeba, a renowned robotics expert and the father of the series' heroine, Shoko Saeba. Before the events of the story, Dr. Saeba was a respected and brilliant scientist. He was abducted by the Tetsumen To, an organization for which he would become the masked leader known as Kaizer. This abduction, however, was a ruse; his disappearance was not a simple kidnapping, as he had been taken to be possessed and controlled by a powerful entity known as the Sigma Computer. Under this influence, the gentle and brilliant scientist was transformed into a calculating and ruthless commander. As Kaizer, he is characterized by his unyielding demeanor and strategic mind, always seen wearing an iron mask that concealed his identity even from his own three henchmen. His primary motivation while under the Sigma Computer's control is to serve its will, which includes capturing the Red Baron robot and his own daughter, Shoko, to further the computer's mysterious objectives.

Within the story, Kaizer performs a dual role. To the world, he is the mysterious and formidable overseer of the Battle Royale competition. He commands his forces, including a series of henchmen, in relentless attempts to seize the Red Baron, issuing orders for the capture of both the machine and its pilot, Ken Kurenai, as well as his own daughter. The dynamic between Kaizer and his daughter, Shoko, is the emotional core of his character arc. She had believed her father to be lost or dead, and his reappearance as a villain is a source of immense shock and pain for her. The revelation of his identity serves as a major turning point in the narrative. Upon seeing his daughter risk her life for her friends, the Sigma Computer's hold on his mind begins to break, and his original personality reasserts itself. Filled with guilt and self-loathing for the crimes he committed while possessed, he confesses everything to Shoko. Despite her pleas for him to return to her, he refuses, believing his only path to redemption is to destroy the Sigma Computer, even at the cost of his own life.

In terms of development, Tetsuo Saeba undergoes a complete transformation from a benevolent scientist to a villainous pawn and finally to a tragic, self-sacrificing hero. His apparent death during the destruction of the Sigma Computer would be his final act of atonement. However, against all odds, he survives the destruction and later resurfaces to assist Ken and the other characters, using his unparalleled knowledge of the Sigma Computer to help them train for the final confrontation. As a scientist, Dr. Tetsuo Saeba was an authority in the field of robotics. As Kaizer, his notable abilities are less about physical prowess and more about his strategic leadership and command over a vast organization. His true strength lies in his scientific genius, which becomes invaluable in the final episodes for understanding and combating the Sigma Computer, highlighting that his most potent ability was always his intellect.