Kaori Sakiyama is a twenty-year-old woman from Hokkaido who stands 179 centimeters tall. She is a self-proclaimed future supermodel who enters the entertainment industry, though her financial struggles are a recurring theme, as she often takes various part-time jobs and lives in a home where utilities are sometimes cut off. Her first appearance occurs while she is working as a model at a swimming pool, where she encounters the protagonist Maki Aikawa. Jealous that all the attention is on Maki, she challenges her, which leads to a misunderstanding and her first real street fight. This event marks her entry into the world of street fighting.

Kaori has a proud and condescending personality and hates being ignored or losing. She is loud, overly dramatic, and prone to hysterical outbursts and screaming. Despite her rough exterior, she has a tidy side to her character, hating being in debt, and often shows a mature, elder-sister-like attitude when looking after Maki and the others. A running aspect of her character is that many people refer to her by her full name in a dramatic fashion, a trait she also exhibits. When enraged, her appearance has been compared to Devilman, as she essentially becomes a berserker powered by her own rage and refuses to admit defeat unless violently knocked unconscious.

Her primary motivation stems from a powerful desire to be recognized by Maki. This evolves into an obsessive, one-sided rivalry where she frequently asks for a match. She works out tirelessly, running and doing tire training, all in an effort to become strong enough to defeat Maki and earn her respect. Deep down, she knows she is no match for Maki but fears being forgotten by her due to her own weakness. This strong feeling ultimately leaves a deep impression on Maki.

Throughout the story, Kaori serves as both a recurring rival to Maki and a close friend who worries about her. She later becomes a professional wrestler and part of a tag team called the Fami-Wrestlers. Her role extends to being one of the first true friends Maki has ever known, as she cheers Maki on from the sidelines during critical battles. In one instance, she takes on the role of Empress Cockroach, the villain in the High Rangers hero show, to help revive a dumbfounded Maki.

In terms of relationships, her dynamic with Maki Aikawa is central, as she is jealous of her yet also caring towards her. She is grateful to Renge for saving her life during a fight where Maki nearly killed her in a mutual frenzy. She also has a painful past involving a former rival from high school, Hanami Matoba, who she later gets revenge on in the wrestling ring. She is shown to be on friendly terms with Maki's other friends and has interactions with various street fighters and wrestlers.

Kaori develops significantly from a relatively weak beginner to a moderately good fighter who accomplishes feats through sheer force of will and determination. Her fighting style is based on long-hit Tai Chi, which she initially took up for dieting but then adapted for fighting. Her primary technique is to spill an opponent's attacks and strike back. Later, she learns a technique called the penetrating goggles, or binoculars, from a character named Yasaki, though she is still immature in handling the required ki and can only use it successfully part of the time. She has a notable background, having served as a student council president in the past, and due to a childhood incident, she is deaf in her right ear. Her determination is best illustrated in a final battle where, although she is knocked out before hearing Maki say she will never forget her, Maki respected her enough to fight with all her strength and without sympathy.