Muteki Choujin Zambot 3

Descendants of a world destroyed by Gaizok, the Jin, Kamie, and Kamikita families have made Earth their home. When the enemy follows, their children pilot vehicles that combine into Zambot 3, their greatest hope of defending the planet.

Protection does not bring gratitude alone. Civilians blame the families for attracting the invasion and its destruction, leaving the defenders to face both mechanical monsters and the resentment of those they are trying to save.