Clara (クレア) is "Hunter Q" who serves in the USNA's Magician Unit "Stardust".  Q means the 17th of the tracking units. 
Clara and Rachel were sent to capture or kill Charles Sullivan code named "Demus Second" who was a fugitive. They initially had split up from Angie Sirius as they had spotted another person along with Charles Sullivan hence forming two teams. They ended up helping track him down and wound him to the point where Angie Sirius was able to shoot a bullet reinforced with Data Fortification to pierce through his defenses, destroying his heart.