In the 2002 OVA Mazinkaiser, Tetsuya fights alongside Kouji against Doctor Hell's forces. The OVA version of Great Mazinger is physically identical to the original, but with black coloring on the arms and legs instead of blue. Great is seriously damaged during the initial battle in the series. It became worse when the captured Mazinger Z attacks the Photon Power Labs even though Tetsuya does his best to defend the lab against Mazinger Z. Lastly, the rampaging Mazinkaiser leaves him badly injured while Great Mazinger is a complete wreck. Consequently, he leaves together with Jun to treat for his injuries.

Near the end of the OVA, Tetsuya returns with a new and much more powerful Great, which is discovered in Doctor Juzo Kabuto's laboratory. This is said to be the real Great Mazinger (or "Shin Great Mazinger"). The "true" Great is structurally the same as the earlier version, but the color scheme for the forearms and legs is blue, as in the original 70's version. It is explained that the Great Mazinger made by Doctor Kenzo Kabuto (Kouji's father) is the prototype version seen in the early episodes, whereas Doctor Juzo Kabuto (Kouji's grandfather), who secretly works in an underground laboratory, managed to finish the final version of Great Mazinger. With a tremendous power compared to the prototype version, Tetsuya asked Kouji to confront Dr. Hell in Bardos Island. Kouji, without knowing the true Shin Great Mazinger, was worried and asked Tetsuya if he can handle an entire army of super robots. However, having the confidence with Shin Great Mazinger, Tetusya scolds Kouji of his cockiness. Therefore, Kouji flies off to fight Dr. Hell leaving Tetsuya against an entire army of mechanical beasts. Consequently, Shin Great Mazinger defeated the entire army of Doctor Hell including the possessed Venus Ace (although most of the battle was not shown). After the battle without damage, Great Mazinger decided to find and help Kouji in the Floating Fortress of Dr. Hell. The concept of Shin Great Mazinger is to bring Great Mazinger to the ranks of modern and more powerful robots such as Mazinkaiser and Shin Getter Robo.