Ayumi Himekawa is a central character known for being the greatest rival to the protagonist, Maya Kitajima. She is the honor-bound and noble daughter of Mitsugu Himekawa, a successful director and producer, and Utako Himekawa, a very famous actress who was once a student of the legendary Chigusa Tsukikage. Touted as a prodigy from an early age, Ayumi has long blonde hair and blue eyes, and is recognized for her beauty and aristocratic bearing. A pivotal moment in her childhood occurred when she discovered that her first acting role was given to her solely because of her family connections. This realization instilled in her a powerful drive to shine on her own merits, leading her to reject any form of arrogance or unearned advantage. She is ambitious enough to aim to surpass her own mother, a widely recognized actress, and people have joked that she will one day steal the role of the Crimson Goddess from Utako.

Ayumi's personality is defined by her confidence, discipline, and unwavering pride in her craft. She has a self-assured belief in her own abilities, famously stating that while others may believe in God when it comes to acting, she believes in herself. Despite her privileged upbringing in a wealthy environment, she is not portrayed as particularly arrogant. Instead, she possesses a strong sense of honor and respects talent even in her rivals. Her primary motivation is to revitalize the renowned role of the Crimson Goddess, and she believes that she must earn this part through her own skill and experience. To achieve this, she takes it upon herself to seek out any role, including minor ones, to broaden her abilities. Her passion for acting is so undeniable that she is willing to undertake extreme measures for artistic authenticity, such as practicing pantomime until exhausted or restricting her diet to appear malnourished for a part.

In the story, Ayumi serves as the primary rival and a constant source of both inspiration and frustration for Maya Kitajima. Their dynamic tension is fueled by their contrasting approaches to acting and their different backgrounds. Ayumi becomes aware of Maya's prodigious gift for acting when they first meet in a practice session, and from then on, she views the younger girl as a life-rival. While critics often favor Ayumi's polished and technically precise performances, she is privately upset at being unable to reach the sort of raw, emotional peaks that Maya instinctively achieves on stage. Their rivalry pushes both actresses to excel; Ayumi relies on precision and control, whereas Maya embraces spontaneity and emotional vulnerability. For Ayumi, Maya is the only person who truly understands her, and she has admitted to feeling envious of Maya for having friends who offer sincere comfort.

Key relationships heavily influence Ayumi's journey. Her bond with her mother, Utako, is complex, as she both seeks to surpass her and feels the weight of her legacy. Her interactions with the photographer Peter Hamill develop into a tentative romantic connection when he discovers her secret struggle and aids her by staging public appearances to deflect media scrutiny. Her relationship with Maya evolves from simple rivalry into a deeper mutual respect, with Ayumi encouraging Maya when she loses confidence and seeing her as a fateful opponent who brings out her best.

Throughout the series, Ayumi undergoes significant development, transforming from a technically flawless actress who relies on precision into one who learns to embrace vulnerability and inner depth. Her dedication is showcased when she is cast as the vengeful Princess of Winter in The Two Princesses opposite Maya's Princess of Spring. Despite being miscast in appearance, she isolated herself in a dark cell to embody the character's emotional desolation. Later, while rehearsing for The Crimson Goddess, Ayumi suffers deteriorating eyesight but refuses immediate surgery, fearing it would cost her the role. She turns this weakness into an artistic strength, rehearsing in darkness to heighten her sensory awareness and imagination. Her condition worsens to the point of risking permanent blindness, yet she persists in performing, determined to prove her capability without medical intervention until after the trial show. This crisis deepens her self-awareness and solidifies her transformation.

Ayumi possesses several notable abilities. Beyond her natural acting talent, she is highly skilled in ballet, classical dance, and piano, with abilities that could make her a professional in any of those fields. She even cooks very well, having learned from a famous culinary researcher, and she maintains top grades in school despite her busy career. Her acting approach is technical and methodical, focusing on how to play a role well through rigorous training and adaptation. She demonstrated her willingness to defy expectations during a performance as Tom in The Prince and the Pauper, where she won over children by begging for money in a hat and accepting their candy, an act of improvisation that surprised those who thought such things would be beneath her. Her ability to lose herself in a role and overcome physical limitations, such as her deteriorating eyesight, by relying on imagination and other senses showcases her profound dedication and resilience as a performer.