In the Universal Century year 0079, the space colony known as Side 3 proclaims independence as the Principality of Zeon and declares war on the Earth Federation. One year later, they are locked in a fierce battle for the Thunderbolt Sector, an area of space scarred by the wreckage of destroyed colonies.

The battle for the Nanyang Alliance's Taal volcano base is over. Sojo Levan Fu and his followers managed to evacuate the newly manufactured Psycho Zakus into orbit. But this victory came at a heavy price. During a ferocious rearguard action, Io--consumed by his bloodlust--accidentally killed someone dear to both he and Daryl. Enraged, Daryl destroyed the Spartan. In the aftermath of the battle, what's left of the Spartan's crew regroups to lick their wounds. Io lies in the infirmary, broken by what he's done. But the war is not finished with Io Fleming, and will leave him with nothing when it's over. Until then, he has only one job to do...