The prologue of the first video showcases the original Getter Robo team taking on an army of monsters in the ruins of New York.
Seeing his friends are about to be overrun, Musashi in Getter 3, rips out the Getter reactor from his mecha and crushes it,
resulting in a very, very, large getter ray explosion.
Fast forward to several years later, when lead Getter pilot Gou is wrestling people in open matches.
One of his opponents turns out to be much more than human and mutates into a huge monster.
Fortunately, former lead pilot Hayato Jin arrives with the Neo Getter machines and his comrades in tow and the battle begins.