All Humongous Mecha Anime male and female lead characters are reincarnations from Kouji Kabuto and Sayaka Yumi.Think about it. How many Hotblooded pilots with Hot-Blooded Sideburns call their robot attacks are there? And how many hot-tempered Tsunderes with short supply of patience love the main character but are always arguing with him and whose robots get inevitably trashed in nearly every battle? And Shin Mazinger Zero manga did not state there were thousands of alternate timelines and worlds and Minerva-X sent Kouji back in time to prevent the end of the world? Obviously she has been sending him and Sayaka through several dimensions, but since they did not exist in some of them, they have reincarnated in the most available candidates (i.e., the Humongous Mecha pilot / Five-Man Band leader and the Tsundere / The Chick). However, a glitch happened in some dimensions, preventing their skills and tempers from manifesting completely and fully, thus diminishing their effectiveness and leading to the extinction of humankind. Final Battle in Great Mazinger he spent the next decades healing his wounds, and rebuilding his damaged face and body. However, when he was fully recovered he noticed that nobody took Humongous Mecha seriously anymore. So he created the Minovsky Particle in order to make giant mecha useful, and he worked for the first sucker he talked into hiring him (given his backstory, he would have no trouble working for someone who thinks that being compared with Hitler is flattering). Unfortunately Zeon granted him a very tight budget, so instead of Robeasts he was forced to build Zakus.