The character from Haibane Renmei sometimes referred to as Raki is named Reki in the series. She is one of the oldest residents of Old Home, the large house where the winged beings called Haibane live, and she serves as its unofficial leader. Because of her seniority, she is the person who welcomes newly born Haibane into the community and takes the main responsibility for helping them adjust to the rules and daily life of the walled town of Glie.

Reki emerged from her cocoon seven years before the main events of the story. Unlike most Haibane, who are born with grey wings, she was born with black wings, a mark associated with the condition known as being Sin-Bound. When her unusual wings were discovered, the older Haibane Kuramori took her to the temple, where it was found that Reki could not remember the full details of the dream she had inside her cocoon, the dream that normally gives a Haibane their name and hints at their past. Her name, Reki, comes from this dream and is connected to the image of small stones scattered on a path. Later in the story, the Communicator, the masked leader of the Haibane Renmei, reveals that her name also carries a much darker meaning related to being torn or crushed, an interpretation that reflects the guilt and self-blame she has carried since her birth.

On the surface, Reki appears cheerful, calm, and reassuring. She speaks casually, teases the younger residents, and creates a warm atmosphere in the household. Beneath this outward warmth, she is an emotionally guarded person with a strong sense of responsibility and a habit of handling problems alone. She rarely talks about her own pain and tends to keep an emotional distance from others, partly out of protectiveness and partly from a deep fear that trusting people will only lead to being abandoned. She can be tough and direct when the situation calls for it, but her firmness usually serves a caring purpose, whether shielding the household from outside scrutiny or keeping a frightened new arrival grounded.

Reki's central motivation is to make sure the Haibane of Old Home, especially newly arrived ones, are safe, settled, and able to adapt. She guides new feathers through their early days, explains the customs of the town and the Renmei, and works to preserve the stability of the household. Her devotion to others also has a private dimension. Because she believes her own condition makes her unworthy of salvation, she pours her energy into helping others as a way of compensating for a past she feels she cannot change. She is reluctant to ask for help herself, because asking for help means risking rejection, and that is the thing she fears most.

Within the story, Reki acts as a senior figure, mentor, and surrogate caregiver at Old Home. Her most important narrative role is her relationship with Rakka, the central character. Reki is present when Rakka's cocoon appears, stays by her side during the painful growth of her wings, gives her a name, and looks after her as she learns to live in Glie. As the series progresses, Reki's hidden past gradually comes to light, and the later episodes center on her own need for salvation. She is forced to recognize that her constant caretaking, although genuine, has also been a way of hiding her true self and avoiding the risk of trusting anyone completely.

The most significant relationship in Reki's life is with Rakka. It begins as a bond between mentor and student but deepens into something more mutual. Reki protects and guides Rakka, yet in the end it is Rakka who refuses to let Reki be consumed by her despair. Reki's friendship with Nemu, the other senior resident of Old Home, is built on years of shared history; Nemu is the person who knows Reki best and understands how much she has suffered. Kuramori, the Haibane who raised and cared for Reki when she was young, is the most important figure from her past. Kuramori's Day of Flight, when she departed suddenly without fully explaining herself, left Reki feeling abandoned and convinced that she was not good enough to be trusted with the truth. That experience became the source of her fear of closeness and her belief that she was fundamentally flawed. Reki also has a painful history with Hyoko, a Haibane from the Abandoned Factory. Years earlier the two attempted to escape Glie together, the attempt failed, and Hyoko came away feeling betrayed, which led to lasting tension between the two communities and contributed to Reki's sense of guilt.

Reki's development is the emotional center of the latter half of the series. Although she seems like the most composed person at Old Home, she is privately convinced that she cannot be saved. The revelation of the darker meaning of her name and the worsening of her condition make her inner turmoil visible, as her despair deepens along with the darkness of her wings. Her growth comes not from solving her problems alone but from finally allowing someone to help her. At the story's climax, isolated and on the verge of being lost, Reki cries out for help, and Rakka answers. By accepting that help and allowing herself to be known honestly, Reki breaks free from the cycle of self-punishment that has trapped her. Her wings return to a healthy grey, and she is able to take her Day of Flight, departing Old Home just as other Haibane do.

Reki has no supernatural powers in the conventional sense. Her most distinctive abilities are emotional rather than physical: she has a keen sensitivity to the feelings of others and a talent for offering comfort, guidance, and stability. She is also a dedicated artist. She spends much of her time painting a mural on the wall of her room, and the unfinished painting gradually reveals itself to be an expression of her inner struggle, containing images tied to her hidden memories and suffering. Through this artwork, she works through feelings she cannot put into words. Within the household, her practical competence, steady presence, and willingness to take responsibility for others are what make her essential to the community.