Kana Arima is a central figure in the story, introduced as a former child prodigy whose career in the entertainment industry began at the very young age of four. She was once celebrated with the nickname "a genius child actor who can cry in ten seconds," a testament to her remarkable emotional control and natural talent that made her a household name. However, this early peak was followed by a significant decline. Her initial success led to an arrogant and condescending attitude towards those she worked with, which, combined with the awkwardness of aging out of child roles, caused her to become known as a "has-been" and job offers to dry up. This fall from grace forced her to adapt, and she developed a new, more cooperative acting style to survive in the industry, often holding back her own brilliance to make her co-stars look better.

In terms of personality, Kana projects a strong and often prickly exterior. She can be acrid and overly honest, which sometimes makes people uncomfortable, and she is prone to jealousy, particularly in her relationships. This tsundere-like attitude, however, masks profound insecurity and a history of being used and discarded by the industry. Despite this, she possesses a core of genuine kindness and a strong sense of responsibility. She cares deeply about the success of the projects she is involved in, often putting that success above her own fame, and she shows a caring, mentoring side to those she grows close to, even if she struggles to express her feelings openly.

Kana's primary motivation is her deep-seated love for acting. It is the central passion of her life, and she longs for the days when she could fully immerse herself in a role and shine on stage or in front of a camera. Her actions are often driven by a desire to reclaim that feeling and to be recognized for her genuine ability rather than being seen as a difficult or fading star. This desire leads her to accept a position as the center of the reformed idol group B-Komachi, alongside Ruby Hoshino and MEM-cho. Although she is initially hesitant and sees idol work as secondary to acting, she agrees to join to help the group and finds a new avenue for her talents as a singer and performer, becoming the de facto leader and center. Her role in the story is that of a multifaceted entertainer—an actress, an idol, and a model—whose journey is about rediscovering her self-worth and learning to stop dimming her own light for the sake of others.

Her relationships with other characters are a key driver of her development. Her life changes course when she reunites with Aquamarine Hoshino and his twin sister Ruby in high school, having first met them during her childhood acting days. Her encounter with Aqua as a child was particularly transformative; witnessing his superior acting ability humbled her and shattered her arrogance, leaving a lasting impression that subconsciously caused her to limit her own performances. As a teenager, she develops strong romantic feelings for Aqua, though these feelings are largely unrequited and become a source of emotional turmoil for her. Her relationship with Ruby is complex, marked by admiration for Ruby's bright, uninhibited personality but also tinged with jealousy, especially when Ruby's popularity as an idol outshines her own. Despite this friction, Kana acts as a mentor to Ruby, helping her with acting and providing crucial support. She also shares a significant rivalry with fellow actress Akane Kurokawa, as they hold opposing views on acting, leading to intense confrontations in their performances and a mutual respect born from their competitive dynamic.

Throughout the narrative, Kana demonstrates significant character development. She starts as an arrogant child, becomes a self-deprecating and insecure teenager who suppresses her talents to be "easy to work with," and gradually begins to regain her former confidence and shed the restrictions she placed on herself. The combination of her rivalry with Akane, her relationships with Aqua and Ruby, and her experiences as an idol all contribute to her growth, allowing her to once again aim for the spotlight on her own terms. Her notable abilities are extensive. As an actress, she masters techniques like the Stanislavski method for emotional recall and the Meisner technique for adapting to scene partners. While she lacked confidence in her singing voice, which she considered distractible, she worked hard to improve and became a proficient singer and dancer, scoring highly in karaoke. Her greatest talent, however, might simply be her natural presence—an ability to shine as brightly as the sun when she allows herself to, making her a captivating performer in any medium.