Sergeant J. Kirby is a Trooper in the Mobile Infantry. Sergeant Kirby was in Colonel Rico's unit on Roku San before and during the Battle of Roku San; She was in the command bunker when the roof caved in trapping all beneath. Luckily, Rico's team survived, but Roku San was lost. Rico was blamed for this disaster but was saved from execution by his friend General Dix Hauser.