During season 2 (The Second Raid), Chidori is being monitored from afar by a man who we later learn is an intelligence operative by the codename of Wraith. After Sousuke is reassigned, Chidori gets the drop on Wraith and confronts him, but is later shot by Xia Yu Lan.
After Leonard turns up and kills Xia Yu Lan, we find out Wraith isn't dead but that the bullet to the head ripped apart a mask. We see what looks to be a female eye. After the conclusion of the Hong Kong incident, the Mithril intelligence agent who was working with the SRT is talking to a woman who wasn't around before. At the very end, when Sousuke returns to school, this same woman is watching Chidori and Sousuke from afar. Her comments lead us to believe she is Wraith.
Why did Wraith pose as a guy? Was there any benefit to her mission in making people believe she was the opposite gender?