Mazinkaiser: Legend of a New Majin

Mazinkaiser: Legend of a New Majin is a one-shot manga by Go Nagai published in September 2001, that tells an alternate interpretation to the battle between Dr. Hell and the Photon Lab. It also gives new interpretations of Juzo Kabuto, Dr. Hell, and Baron Ashura. Some of the background settings and use of the Mycenae Empire being aliens who came to Earth was later used in Shin Mazinger Shogeki! Z Hen.

Plot
Dr. Hell is with the Iron Masks overlooking the recovery of Baron Ashura planning to mobilize his army of Mechanical Beasts soon. At another area Koji looks at the remains of the destroyed Mazinger Z before Sayaka catches up with him. She explains that she would like to fight again with Aphrodite, but Koji moves away telling her not to as he wouldn't be there to protect her. As Koji rides, he encounters Baron Ashura but this being is different from the one he fought time and again as he/she has the dual gendered bodies in a reversed state. This alternate Baron Ashura then takes Koji to a scientist by the name of Dr. Heaven. Dr. Heaven then introduces himself as the true Juzo Kabuto, explaining to Koji that the man who built Mazinger Z was a clone of him, as was Dr. Hell. The clones worked together to uncover the mysteries of the ancient alien civilization the Mycenae Empire. However, the clone that became Dr. Hell grew more ambitious and decided to take the power and technology for himself to rule the world. As the original Juzo went into hiding, the clone went to work on the Mazinger Z and met his fate. Now the true Juzo Kabuto gives Koji a new and more powerful robot to combat Dr. Hell and his Mechanical Beasts, which he calls a true god: Mazinkaiser. With this new robot, Koji rides off into battle.