After suffering unexplained injuries, Chall Acustica left Celestial Being, where they were once a Gundam Meister. They joined forces with Fereshte in their fight against war, and welcomed the rebellious 18-year-old Fon Spaak. Despite being coerced into piloting the GNY-004 Gundam Plutone as part of illegal activities, Fon's tutelage under Chall Acustica has given him newfound purpose in fighting for a noble cause.