Years after the climactic battle against the Sol Masters, Mamoru and Kaidou continue to protect Earth and its citizens from all kinds of threats. However, with the rest of the GGG stuck in space after their victory, many mysteries remain, and their fate is unknown.

The current GGG and the government work together to set up Project Z, an attempt to save the lives of the old Gutsy Galaxy Guard crew. However, nothing is certain, and new challenges must be faced.