Great Mazinger tai Getter Robo G: Kuuchuu Daigekitotsu

In an alternate timeline, Getter Robo is destroyed by aliens. As they work to activate Getter Robo G with Saotome, Great Mazinger and Venus A get involved, keeping the aliens at bay. Great Mazinger's Booster continues to be worked on in the background. Both teams work together keeping the aliens busy as they get their best weapons operational.