Childhood at the Insitute
During her childhood, Citrine wasn't allowed to remain with the male U.R.T.V.s, but only with the others female U.R.T.V.s, and could only meet Yuriev and his coworker. The three male variant met her for the first time about at the same time they did the mission inside of Sakura's subconscious,, surprising them, Albedo having only heard of a girl room, without knowning if such room actually existed. At this time, she shown herself as very arrogant, and claimed the females U.R.T.V.s were theoretically more powerful than the male U.R.T.Vs. Rubedo looked irritated at her when she claimed the others female who died had been "disposed of", due to the instability coming when a female URTV is created, and he asked her who she think she is, a question she returned to him without replying.
Missions
She had a discussion with Nigredo latter on, and she taught to him that they had basically the same powers, and explained why they both didn't have normal Anti U-DO waves: in order to control the Red Dragon, Rubedo's ability, if ever it went out of control. She was allowed latter on to, exceptionally, follow the boys in their mission into Sakura Subconscious, this being likely the only time she did a mission with males U.R.T.V.s. There she saved Nigredo's life when he was in danger, and help Rubedo to defeat a contaminated URTV, what surprised the others boys, at first view they didn't think she'd care about protecting them from anything.
On the Old Miltia
She went with the boys to the Old Miltia, and she saved Nigredo once more, from the attack done by a soldier. She collapse following a wound at the head she receives at this moment, but doesn't seem deadly touched. After this, Rubedo worries for her and does not focus enough on the link to destroy U-DO, until the moment he realizes what Yuriev planned and breaks the link. It is unknown what happend to Citrine, but she was likely rescued by the Salvator Faction of the Federation.