Kazane was raised by her mother Kaname who frequently traveled overseas for work. Raised separately from her half-brother, Shinra, Kazane develops an interest in him after her mother tells her of his existence when she was in elementary school. Since then, she frequently travels as far as Ikebukuro and observe him from afar in an attempt to get to know him.
Five years prior to the start of the series, she had encountered Masaomi Kida and inadvertently helped to name his future gang, the Yellow Scarves, after noticing Masaomi's dyed yellow scarf and mentioning the Yellow Scarf Rebellion.
While she was in high school, she was bullied by some men who thought she was a whore for Izaya. She was saved by Kururi and Mairu. They warn her to stay away from Izaya and she tells them she is Shinra's sister. She promises to give the her thanks the next time she sees them.
Upon spotting Shingen, she decides to follow him so that she can understand him better as well. She adds him to her list of "observations," curious of her half-brother's father and why he wears a mask. One of the days when she is out observing him discretely, she is sedated by Emilia Kishitani, who was ordered to capture her by Nebula in case she was a spy, and brought to one of Nebula's laboratories to be interrogated. By the time she regains consciousness, Emilia had already down a background check and learned of her connection to her husband's family. Kazane is then asked if her mother is using her to seek reconciliation with Shingen. Kazane dispels Emilia's concerns and clears up the misunderstandings. The two discuss Shingen, leading Emilia to retell how she met her husband as well as their encounters with the supernatural correlated with it. Kazane tries to make Emilia give her information on the Headless Rider, but Emilia refuses and tells her to keep what they had discussed a secret, realizing she spoke too much. Kazane is let go to continue her usual activities.
One day she is approached by her boss to find information on the local gangs for an article, specifically the Dollars. Kazane takes the job, half for work and half out of personal interest. She finds and follows members of the Blue Squares to get information, but the boys took notice of her and she is taken to their hideout where she meets their leader, Mikado Ryuugamine. Mikado is initially unconscious when she is brought to the hideout, having been knocked out from an earlier fight, and when Mikado awakens Kazane is questioned for why she was investigating them. Kazane is upfront with Mikado, afraid of what he might do, stating she wanted to know their connection with the Headless Rider. Mikado seems to become less weary of her hearing that and admits how much the Headless Rider had influenced him and the actions he is taking now.
After the two talk, Mikado has his friends drop Kazane off along Kawagoe Highway unharmed. Kazane begins to walk home and ponders what she could do to help Mikado, worried what trouble the boy was getting into. Just as she decides to contact the Headless Rider for help, she is attacked by other hoodlums who had seen her get dropped off by the Blue Squares. They try to kidnap her, but she is rescued by Chikage Rokujou who had been passing by. Chikage knocks the men unconscious and checks to make sure Kazane is alright. Shortly after, Chikage's girlfriends find them. Non berates Chikage for being so reckless, mentioning how he got beaten up by Shizuo Heiwajima. When Kazane hears Shizuo's name, she asks Chikage how he is affiliated with him. Surprised, Chikage asks if Kazane knew of Kyouhei Kadota as well, to which Kazane informs him of Kyouhei's recent hospitalization. After Kazane gives Chikage the place Kyouhei is being treated at, Chikage leaves Kazane with his girlfriends and requests them to escort Kazane back home.
The following day, Kazane goes to Raira Hospital to visit Kyouhei as well as see Chikage and his friends again. As she is heading there she encounters Izaya Orihara in front of the hospital. Izaya proceeds to mock her for her inability to meet her brother despite giving her a chance back when they had first met, but what Izaya proposed as a possible reason why she has been avoiding to meet her brother actually was a relief to Kazane, giving her more confidence. She thanks Izaya for helping her come to this realization, but Izaya informs her of Shinra's state and severe injuries. After Kazane talked with Izaya, she heads inside the hospital to visit Kyouhei, all while worried for her brother and what condition he must be in. While she sat in the lobby she is approached by Kasane Kujiragi, who knows of her relation to Shinra and suggests they talk.
- Kazane's favorite food is sweet potatoes.