Beneath a bug-ravaged world, the upper city controls energy and mecha might, leaving the lower city to scrape by. Kyle, written off as a nobody, shocks everyone by defeating a royal-class bug on his own and becomes the hidden legend the Alliance wants. His search for his past leads him upward, where he is mocked and dismissed as a false heir. Then danger strikes Mona during the mecha tournament, and Kyle stops holding back. In one moment, the city learns that its "trash" is actually the true Cross heir—and history's most powerful mecha pilot.