After deploying several sleeper agents around the globe, the Vagans launch a surprise attack that finally brings the war to the Earth. To counter the invasion, Flit activates the recently completed Gundam AGE-3 and entrusts it to Kio. Just like his father and grandfather before him, Kio enlists into the Diva as part of its mobile suit squad to confront the Vagans.

(Source: Gundam Wikia)