Kaede Fuyou is a central figure in the narrative, serving as the childhood friend and classmate of the protagonist, Rin Tsuchimi. She is widely regarded as an exceptionally gifted individual, excelling in academics, sports, and housework, and is known for her polite and modest demeanor. Her striking appearance, characterized by shoulder-length orange hair and blue eyes, contributes to her immense popularity at school, where she is often called the "Princess of the Human World" and has an unofficial fan club among the male students.

Beneath this composed and perfect exterior lies a deeply complex and troubled personality, forged by a traumatic past. Kaede's history is defined by a tragic car accident that claimed the lives of her mother and Rin's parents when they were children. Overwhelmed by grief and unable to cope, the young Kaede lost her will to live. In a desperate act to save her, Rin falsely claimed responsibility for the accident, giving Kaede a target for her anguish and a reason to live: revenge. This lie led to years of brutal mistreatment, during which Kaede subjected Rin to relentless psychological and physical abuse, secretly orchestrating campaigns of bullying and even attempting to harm him directly. The truth of Rin's sacrifice was eventually revealed, causing Kaede to collapse under the weight of immense guilt and remorse for her actions.

This revelation marks a pivotal turning point, transforming her hatred into an obsessive, all-consuming devotion. To atone for her past, Kaede dedicates her entire existence to serving Rin. She takes complete charge of all household duties, from cooking his meals to waking him each morning, and becomes deeply distressed whenever Rin tries to help, believing it would rob her life of its meaning. Her motivation is driven by a profound sense of unworthiness, as she feels she does not deserve Rin's love or even the right to stand by his side. Despite her romantic feelings for him, this guilt is a constant barrier, leading her to declare herself his property rather than an equal partner.

Her role in the story is that of the devoted, ever-present childhood friend whose stability is threatened by external forces. She is frequently seen caring for Rin and their household, which also includes the mysterious girl Primula. Her key relationships are heavily defined by her fixation on Rin. This creates significant friction with other heroines, particularly with the upperclassman Asa Shigure. In the anime adaptation, Kaede's obsessive love and fear of abandonment manifest as explosive yandere tendencies. When she perceives that Rin's affections are shifting towards Asa, her mental state deteriorates visibly, leading to episodes of extreme jealousy, violent outbursts, and a menacing, hollow-eyed stare.

Kaede's character development is a tragic arc from a pure, loving child to a grief-stricken avenger, and finally to a guilt-ridden caretaker whose life revolves entirely around another person. While she manages to overcome her hatred, she remains trapped in a cycle of self-imposed servitude as penance, struggling to see a future where she can be happy with Rin without feeling she is taking something undeserved. Among her most notable abilities are her near-superhuman domestic skills, which she perfected specifically to please Rin, as well as her high academic and athletic prowess, which make her a formidable and admired figure at school.