Mira Kudan is a whispered girl that Sousuke rescues right in the very beginning. When Mithril is destroyed, she goes into hiding along with Wraith and Hunter in Alaska. With the help of AL, the original AI system in the Arbalest, she builds the ARX-8 Laevatein. In the novel translation, she is called Sarah Miller.

Sousuke Sagara, a seventeen year old military specialist working for the secret organization MITHRIL, has been assigned to protect the latest "Whispered" candidate Kaname Chidori. To complete this task Sousuke will have to deal with enemies from his past as well as the occasional panty thief. Unfortunately for Sousuke, the toughest part of his mission isn't only protecting Miss Chidori but also getting used to living an average High School students life, no easy task for someone raised on the battlefield. 
(Source: Anime News Network)

Nine months have passed since teen soldier Sousuke Sagara first became Kaname Chidori's covert protector. In that time, Mithril has been remarkably successful at thwarting Amalgam's efforts, but this has only made Amalgam more determined. Leonard Testarossa's visits with Tessa and Kaname are just preludes to all-out attacks that begin with global communications disruptions. Kaname's status as a Whispered makes her one of Amalgam's main targets, which means that any semblance of a peaceful life at Jindai Municipal High School is now over for her.
 
(Source: Anime News Network)

Jindai High School was a relatively safe place, right up until Sousuke Sagaka transferred there. A total nut, he wreaks havoc on the school's student body and gets into a world of trouble with the teachers! But there's more to Sousuke than meets the eye&mdash;not just a hell-raising student, he's actually a member of an elite military unit, on an undercover mission to protect the beautiful schoolgirl Kaname Chidori from the KGB. 
(Source: Tokyopop)