Furau is a hikikomori or "shut-in" otaku. She is in charge of the "GUNVARREL KILL-BALLAD On-Line" program.
Frau was the daughter of Minami Kogori who is the anime director of Gunvarrel series, and when the 13 staff members were mysteriously killed and Minami was nowhere to be found, Frau had to hide herself.
In the time after her mother had died, Frau became a shut-in in order to concentrate on creating an online game for Gunvarrel. She felt that if people had forgotten Gunvarrel, her mother's creation, her mother's memory would disappear forever. So, she enlisted a group of friends on the internet and created what was soon to be called "Kill Ballad Online."
Frau Koujiro is created by 5pb, and she has no information regarding any inspiration used to create her. She first appears in Robotic;Notes visual novel game and makes her first anime debut in episode 1. Frau is voiced by Kaori Nazuka.
She can be random with her moods, but she is passionate about the Kill Ballad Online game.
While outside, Frau tends to wear her school uniform which comes in a white and blue version. She also has her hair tied up so that it forms two gravity defying pigtails. When at home, she lets her hair down and wears pajamas.
Originally, Frau had brown hair, but it appears that she has dyed it blond from the time frame between the day her mother disappeared to the series' present day.
Minami Kogori - Minami is Frau's mother. Through flashbacks it has been shown that the two were very close. After her mother had died, Frau had become to a shut in to create a memento in order to remember her mother.
Subaru Hidaka - Initially, Frau did not want to do anything with Subaru until he mentioned that he helping Kaito. Since then Subaru has been a common person in perverted daydreams about Kaito.
Kaito Yashio - Kaito and Frau had first met online in the Kill Ballad game. In the past, she has helped him by giving him the codes to enable the Kill Ballad controls for his hobby robot. Since then, Frau his enlisted Kaito in her quest to ban all hackers in the Kill Ballad online game. After Kaito has stopped the robot malfunction in Tokyo, Frau might have developed romantic feelings towards him. This is revealed when Frau kisses Kaito for helping find the hackers and save her committing suicide.
Airi - Frau has a strong interest in loli girls; she finds them to be very cute. Whenever Airi appears on Kaito's phone, she likes to snatch it and make googly eyes at Airi. Before Airi's "death", Frau had sent her virtual snow to make Airi happy as a farewell gift.
She is mentioned when Kaito calls her to help him change the control of Tanegashi Machine to Kill Ballad Online's controls. She is seen at the airport where she smiles at Kaito before leaving him and Akiho.
Since Frau helped Kaito with transferring the Kill Ballad codes, she has Kaito move her stuff into her new place. When Subaru asks Frau to help him out, Frau tries to shoo him away. When Subaru asks Frau a second time to help him write a program for his hobby robot, Frau has Subaru accept her conditions. Her conditions are that Subaru has to do a nude photo shoot. However, Subaru reminds her about his real promise of having Kaito help Frau to find the cheaters in KILL Ballad.
Later, Frau asks Kaito to come to her home where she instructs Kaito how to track down cheaters using her chip to scan the players during Kaito's battles. As time goes on, she explains to Kaito why Gunvarrel's last episode did not air and the mystery behind the murder of the staff and disappearance of her mother.