Himari Inuzuka is the female protagonist of the story, a seventeen-year-old high school girl known for being a bright and sociable presence among her peers. Her birthday is given as February 24th, though one source lists February 4th. She is recognized at school as an honors student and comes from a distinguished family, carrying herself with an air of elegance and discipline that has made her a figure of admiration for many classmates. Despite this poised and proper public image, Himari possesses a private personality that is far more lively, playful, and averse to boredom, creating a charming gap between her outer perfection and her inner spontaneity. She has a strong dislike for tedious or uninteresting things and is always in search of new challenges and excitement. Her tastes include dairy-based drinks and sweets like yoguruppe.

Himari shares an exceptionally close bond with her classmate Yuu Natsume, a friendship that originated in middle school and is the emotional core of her story. The two are the sole members of their high school's gardening club, a space where they nurture both plants and their shared dream of one day opening a shop together to sell handmade flower accessories. This dream began when Yuu gave Himari a handmade choker in her second year of middle school; touched by his thoughtfulness and craftsmanship, she joined his venture and they vowed to become partners in purpose, or "shin'yuu". As friends, she is physically affectionate and forward, often teasing him with playful pranks and enjoying the easygoing dynamic of their relationship. She values their friendship deeply, although her feelings become complicated by a seeming obliviousness to her own romantic inclinations, a fact she has previously joked about. In the past, she has had several romantic relationships, including one with a boy named Shinji Makishima, but none of these have lasted, and that particular ex-boyfriend continues to orbit her life as a friendly rival for Yuu's attention.

Her primary motivation is to preserve the unique and intimate friendship she shares with Yuu, a relationship she has long relied upon as a constant in her life. This motivation is thrown into sharp relief when Yuu reconnects with a childhood crush, Rion Enomoto. Triggered by the threat this new dynamic poses to her status as Yuu's closest companion, Himari begins to navigate confusing feelings she has never experienced before, forcing her to question whether her bond with Yuu can truly remain platonic.

As the story progresses, her role shifts from that of a cheerful and unwavering best friend to a central figure in a romantic conflict. Her actions in this context are complex and often divisive among audiences. While some view her behavior as a realistic, if messy, portrayal of a teenage girl struggling with deep-seated insecurity, others find her to be manipulative and possessive. She is known to use emotional outbursts, such as threatening to move away to Tokyo, to influence Yuu's decisions and prevent him from prioritizing his own goals or other relationships. When she feels her place in Yuu's life is threatened, she can become a "green-eyed monster," employing tactics to engineer intimate moments with him and subtly undermine her romantic rival, Rion. Her behavior hits a notable low when she publicly humiliates Yuu and declares their friendship over, an act for which she never apologizes. Despite these unhealthy tendencies, many see her as an ultimately sympathetic figure whose impulsive and immature actions stem from genuine fear and vulnerability rather than malice. Over the course of the narrative, her character shows signs of growth, becoming more grounded and relatable as she gains a clearer understanding of her own heart and the consequences of her actions.

Himari's key relationship is undeniably with Yuu Natsume, an individual whose passive and forgiving nature often enables her problematic behavior, as he consistently forgives her transgressions and fails to set firm boundaries. This dynamic creates a co-dependent circle where her manipulation and his submission feed into each other. In contrast, her relationship with her older brother, Hibari, serves as a crucial corrective force. He acts as the voice of reason within the story, not hesitating to call out Himari for her toxic and wishy-washy attitude, often delivering harsh truths that reduce her to tears. Her connection with Rion Enomoto is that of a complicated rival; initially, Himari displays a subtle cruelty by mockingly trying to set Rion up with Yuu, convinced he will remain loyal to her, but this plan backfires spectacularly. Her notable abilities include an innate charm that can make anyone smile, a sharp wit to match her verbal sparring with rivals like Rion, and practical skills in gardening and supporting the creation of flower accessories, which are central to her partnership with Yuu.