Yuki

セクサロイド・ユキ

Yuki technically lacks a surname, but she is designated as a sexaroid (a nod to the character creator's earliest work of the same name, and a term for the type of robotic humanoid she belongs to). She serves as the medical officer for Sirius Platoon.
Her behavior does not readily reveal her robotic origins, but for much of the first season, she does not view herself as particularly human. Consequently, she avoids certain human mannerisms, such as socializing, preferring to live solely for her duty as the medical officer of the Big 1. However, after Manabu saves her life while she is pursuing a group of wanted criminals, she allows herself to be persuaded to participate in social events.
Yuki's personality is generally calm and somewhat withdrawn, though not devoid of a certain sense of curiosity (especially following the aforementioned incident). She places little value on her own life and is prone to making rash decisions in emergencies whenever a humanoid life is threatened, dismissing her actions with the reasoning that she "can be replaced if something were to happen."
Nevertheless, she seems to enjoy her work, and she once professed a certain affection for Manabu, who looked like someone she had known in the past—possibly her creator.