The villainous Dr. Hell has amassed an army of mechanical beasts in his secret hideaway, the island of Bardos located in the Aegean Sea. He is capable of controlling mechanized beasts with his cane, and instructs them to unleash devastating attacks. However, Dr. Hell doesn't do all the dirty work by himself; he has his loyal henchman Baron Ashura to carry out his devilish plans.
There are also those that will see to it that evil does not prevail. Kouji Kabuto is the young and feisty teenager with a score to settle: his goal is avenging the murder of his grandfather by Dr. Hell. And he might just be able to pull it off, as he is the pilot of Mazinger Z, a mighty giant robot made out of an indestructible metal known as Super-Alloy Z.
Il professor Juzo Kabuto realizza la Superlega Z, un derivato del Japanium, un elemento scoperto negli strati della zona del Fuji. Il malvagio Dottor Inferno, malvagio ex-collega di Kabuto, intende impossessarsi dell'invenzione per creare il suo personale esercito di mostri al fine di conquistare il mondo. Un commando di soldati assassina l'illustre scienziato ma quest'ultimo riesce a consegnare al nipote Ryo la sua invenzione: Mazinga Z, un potente robot realizzato in superlega Z, l'unica arma in grado di opporsi all'esercito e alle ambizioni del dottor inferno.
Un submarino emerge de las aguas y atraca en una isla repleta de ruinas griegas. Del submarino se baja un ser mitad hombre y mitad mujer llamado Barón Ashler que entra en una cueva donde se reúne con un científico loco, barbudo y con un bastón, llamado Doctor Infierno. El Dr. Infierno le enseña a Ashler su ejercito: tres robots gigantes con los que planea dominar el mundo... si antes consigue eliminar a la única persona que conoce su secreto y puede detenerle: el Doctor Kabuto.
世界征服を企むドクターヘルは、あしゅら男爵に機械獣を操るバードスの杖と海底要塞サルードを与え、邪魔者の天才科学者・兜博士の抹殺を命じた。あしゅら男爵はお手伝いのルミから、博士が別荘に滞在していることを聞き出す。博士の孫・甲児が駆けつけた時は既に遅く、別荘はあしゅら男爵によって爆破されていた。瀕死の重傷を負った兜博士は、ドクターヘルに立ち向かうために建造した秘密兵器・マジンガーZを甲児に託す。
