This is the part where the show stops pretending you're a grown-up. The Armanoid war is settled, the Gallos show up, and Zero Tester quietly reformats itself for a younger crowd: brighter, faster, more robot per episode, less of the slow-burn space-accident dread that opened the whole thing in 1973. Shin, Go and Lisa are still flying out of the Future Science Invention Center under Professor Tachibana and Captain Kenmotsu, three Tester vehicles still slam together into one giant, and the combination sequence carries more weight than the plotting does. Watch it as the missing link it actually is, Sunrise's first TV series learning on the job, with the Thunderbirds rescue-team DNA still visible before the studio figured out what it would do with combining robots later. It's 27 episodes of a franchise deciding who it's for, and being honest about it.

The second season of Zero Tester reveals that a string of space accidents is the work of the Armanoid aliens, who plan to invade Earth. Joined by other world leaders, Professor Tachibana assembles a team at the Future Science Invention Center and readies five cutting-edge vehicles. Shin, Go, Lisa, and Captain Kenmotsu take them into service as the special Zero Tester Squad, formed to meet the coming Armanoid attack. Expect sci-fi mecha action and adventure.