Due to the emotional trauma Karla suffered during the One Year War, her mind has regressed back to that of an adolescent child with the Zeon Remnants now trying to take care of her in hopes of her adult mind to recover. Daryl's Acguy squadron heads to a South Seas Alliance-controlled city in Southeast Asia to retrieve a spy, but their cover is blown and they must fend off against the island's mobile Suits. Meanwhile, the Spartan is confronted by a South Seas Alliance mobile suit Squadron, with Io's former commander and lover Claudia leading them.
Federation troops and Zeon forces carry out a fierce battle in the Thunderbolt Sector in what was once Side 4 "Mua". The Thunderbolt Sector is a shoal zone composed of the debris of destroyed space colonies, named for the electrical discharges from the metal debris. MS pilot Io Flemming is among the Federation soldiers who are dispatched to the area, where Zeon sniper Daryl Lorenz awaits them on the battlefield.
