Kazuki Mikadono is the eldest of the three Mikadono sisters, a family of prodigies who attend the prestigious Saika Academy. She is a third-year student in the performing arts department, where she has already established herself as a rising star. Unlike her sisters, who excel in martial arts and shogi, Kazuki's domain is the stage. She is a celebrated actress and singer, specifically recognized as the lead performer of male roles, known as the otokoyaku, in a popular, all-female theater troupe. Her talent is so profound that she has successfully revived roles that were once considered impossible to perform again, earning her acclaim that extends to international audiences.

In terms of appearance, Kazuki has a tall, slender, and distinctly androgynous figure, standing at 172 centimeters. She has short, neatly styled hair with a blue or purplish tone and sharp, often gold-colored eyes. Her boyish, handsome looks, often described with the term "ikemen," have made her immensely popular among the female students at her school, who admire her as a princely figure. This appearance is complemented by her demeanor and wardrobe, both of which are consistently boyish and polished to fit her public image.

Kazuki's personality is largely defined by her tremendous pride and self-confidence, which are backed by her genuine talent and an overwhelming dedication to her craft. She is an intense perfectionist who sets exceedingly high standards for herself and despises failure. This drive pushes her to train relentlessly, even to the point of practicing while ill with a fever, all to ensure her performances are flawless. However, beneath this proud and sometimes harsh exterior lies a more vulnerable side. She carries the weight of expectation as the eldest daughter and a star performer, feeling a compulsion to lead and support others without ever relying on anyone herself. A quirky and often humorous contrast to her refined stage presence is her extremely picky eating habits; she has a strong dislike for a specific list of foods, including green peppers, shiitake mushrooms, eggplant, bitter melon, and wood ear mushrooms.

Kazuki's primary role in the story is as one of the three heroines, and her initial relationship with the protagonist, Yuu Ayase, is fraught with conflict. When Yuu comes to live with the Mikadono sisters, she looks down on him, scoffs at his lack of talent, and dismisses him as a freeloader, especially given his lineage as the son of a legendary actress. Her cold and dismissive attitude is a significant barrier that Yuu must overcome, making her the hardest of the sisters to win over. Her relationships with her younger sisters, Miwa and Niko, are loving but have become strained due to the oppressive expectations of their father. She cherishes memories of sneaking out with them to festivals when they were children, but in the present, the three have drifted apart, living like strangers under the same roof. When her father returns and threatens to expel Yuu, Kazuki demonstrates her protective loyalty by directly defying him, insisting that Yuu is a blessing who helps them grow, not a hindrance.

The most significant development for Kazuki begins when her stubborn wall against Yuu starts to crumble. This change is catalyzed by two key events. First, when she falls ill from overworking, Yuu persistently cooks for her, eventually breaking through her stubbornness and her picky eating to help her perfect a new acting role. Second, and more pivotally, a domestic accident while washing dishes causes her to slip and accidentally kiss Yuu. This incident sends her into emotional turmoil, making her acutely self-conscious and forcing her to confront unfamiliar romantic feelings. Initially flustered and trying to dismiss the kiss as meaningless, she later grows enraged when Yuu suggests the same. This tension culminates in her boldly asking him on a date, the first among her sisters, during which she becomes more comfortable and ultimately confesses that their kiss was not meaningless after all. Following this event, she becomes noticeably more considerate, beginning to help Yuu with household chores, though she is careful to only assist with tasks she feels she is capable of handling, disguising her kindness with a claim of being in a generous mood.

Kazuki's notable abilities are almost exclusively tied to her performance arts. She is a genius actress and singer, with a commanding stage presence and the versatility to master any male role. Her deep voice and polished appearance are perfectly suited for these parts, and she sells out every performance she appears in. However, a key part of her development involves confronting a new challenge: taking on her first female role in a play, a task that initially makes her doubt her skills despite her prodigious talent. This struggle highlights that her identity as a performer has been narrowly defined, and her growth involves expanding her range with Yuu's support.