Chizuru Yoshida is the main protagonist of the manga series Hen. She is a strikingly beautiful and seemingly perfect high school student who is fully aware of her attractiveness and the effect it has on others. To her peers and the men she encounters, she presents the image of a confident and desirable young woman. Chizuru has a part-time job as a model, which further reinforces her status as someone who excels in the social currency of appearance. Despite her popularity and ease in attracting male attention, her romantic life is characterized by a lack of genuine emotional connection. She engages in several relationships with men, including an inappropriate affair with a teacher, but these encounters leave her feeling empty and unloved.

Chizuru's life and self-perception are completely upended with the arrival of Azumi Yamada, a new transfer student who also becomes her neighbor. In contrast to Chizuru's sophisticated and worldly persona, Azumi is shy, naive, and possesses a childish innocence. Initially, Chizuru reacts to her new feelings of attraction with confusion and denial, mocking Azumi and trying to dismiss her as unremarkable. She has never experienced love before and the intensity of her feelings for another girl forces her to question her entire identity. This internal conflict is a central part of her character, as she struggles to accept that she has fallen for someone so different from the type of people she usually associates with.

Chizuru's primary motivation becomes winning Azumi's affection. After a brief period of denial, she quickly resolves that she must be with Azumi, no matter the cost. This goal drives almost all of her actions throughout the story. Her previous manipulative and cold-hearted behavior begins to change as she experiences genuine emotions like shyness, jealousy, and vulnerability for the first time. She confesses her love to Azumi and longs for a committed relationship, even going so far as to ask for Azumi's hand in marriage on a stage. In her pursuit, she often puts forth every effort to be close to Azumi, even moving into the same apartment building as her, living with a fake boyfriend named Hiroyuki who is a rock star.

In the narrative, Chizuru is the central figure whose emotional journey drives the plot. The story explores her transformation from a promiscuous and emotionally detached femme fatale into someone capable of deep love and commitment. Her key relationships are defined by this change. Her interactions with men, like her boyfriend Hiroyuki, become a way for her to try and convince herself that she is not attracted to Azumi, but she ultimately finds herself fantasizing about Azumi even when she is with him. Her relationship with Azumi is the core of the series, as Azumi is the only person who can make her heart race and for whom she is willing to abandon her old lifestyle. She also becomes part of a love triangle with Azumi and a male student named Ryuichi, who also has feelings for Azumi.

Chizuru undergoes significant development over the course of the manga. She starts as a manipulative alpha bitch who uses her sexuality to control others. Her struggle with her identity is intense and involves a great deal of confusion and self-deception. She has sex repeatedly with her boyfriend in an attempt to reaffirm her heterosexuality, but she ultimately accepts her feelings for Azumi when she realizes she cannot stop thinking about her. By the end of the series, her more loathsome qualities have almost entirely faded. The story concludes with her rejecting a marriage proposal from Hiroyuki in order to be with Azumi, and the two fly off together to start a new life. This resolution cements her development from a character who took advantage of others to one who is willing to sacrifice a conventional future for the sake of true love.

In terms of notable abilities, Chizuru is highly intelligent and manipulative, skills she initially uses to get what she wants from her male lovers. She is also a successful model, indicating a high degree of poise and presentation. Perhaps her most defining trait is her intense and unwavering determination once she sets her mind on a goal, which, in the story, is solely focused on winning Azumi. Her physical appearance, particularly her large bust, is frequently commented on and is a source of her power over others, as it often distracts the male characters.