Dr. Hell returns with his upgraded Mechanical Beasts, posing a heightened threat. Kouji Kabuto and Tetsuya Tsurugi engage in a fierce struggle against these menacing machines led by Baron Ashura. Despite their valor, they suffer defeat, with Kouji's Mazinger Z seized and Tetsuya's Great Mazinger severely crippled. Dr. Hell swiftly transforms the captured robot into Ashura Mazinger, launching an assault on the Photo Power Lab. Meanwhile, with Kouji missing, Tetsuya valiantly defends the lab in his damaged Great Mazinger. Overwhelmed by Dr. Hell's superior forces, even Tetsuya's courage falters, signaling impending doom. As hope wanes, a powerful blast from an unidentified robot obliterates the entire Mechanical Beast army. Could this enigmatic savior be the fabled Mazinkaiser, and who commands this awe-inspiring machine?