Fumino Furuhashi excels in literature and arts as a third-year Ichinose Academy student, earning the title "The Sleeping Beauty of the Literary Forest" for her emotionally resonant writing. Yet she struggles profoundly with mathematics and science, often falling asleep when faced with complex equations. Her university aspiration is astronomy, driven by a belief that a specific star embodies her late mother, Shizuru Furuhashi's spirit. This goal persists despite her mathematical challenges and initial discouragement from her father, Reiji Furuhashi, a mathematics professor. Their relationship fractured a decade ago after Shizuru's death, reducing communication to written notes. A pivotal incident where Reiji compared Fumino unfavorably to her mother cemented lasting emotional distance and a fear of aggressive men.

Tall and slender, Fumino possesses waist-length silky blue hair (dark in manga, bright in anime), typically swept by bangs to the right and secured with a white headband. Her brown eyes and a distinctive beauty mark beneath her left eye contribute to an elegant appearance, cementing her status as one of the school's most admired students. She usually wears a blue school sweater, and her hairstyle varies—featuring ponytails, twin tails, or chignons—though the anime simplifies this to straight hair with occasional ponytails.

Fumino's personality blends cheerful warmth with quiet introspection. She maintains a reserved demeanor, interacting sparingly outside her close friend circle. Nariyuki Yuiga, initially her tutor, becomes her primary male confidant and the sole exception to her fear of aggressive men. Highly attuned to others' emotions, she frequently acts as Nariyuki's advisor on romantic matters involving Rizu Ogata and Uruka Takemoto. This role complicates her own developing feelings for him, which she suppresses to protect her friends. She exhibits excitement for astronomy and zodiac signs, often stargazing, yet displays reluctance toward social performances like school plays where she is often cast as a heroine. Additional traits include left-handedness, self-consciousness about her appearance and household skills, a love for sweet and spicy foods, and poor cooking ability.

Her affluent background was marked by her father's academic focus and emotional neglect after her mother's death. A pivotal development occurs when she and Nariyuki discover a password-protected folder on her mother's old laptop. Successfully deducing the password as her father's name, they uncover a video message from Shizuru, facilitating a heartfelt reconciliation. Reiji acknowledges regret over their estrangement and eventually accepts Nariyuki's positive influence. This strengthens Fumino's resolve for astronomy and deepens her emotional bond with Nariyuki.

Her character development intertwines with Nariyuki across various storylines. She frequently serves as his emotional consultant, and their relationship evolves through shared experiences like multiple stargazing dates and accidental situations, including sharing an inn room due to missed transportation. They also temporarily live together to avoid her father, leading to domestic interactions that blur their student-tutor dynamic. During a school festival play, she inadvertently kisses Nariyuki while he wears a cat costume mask, initiating the act unaware of his identity. In her dedicated conclusion, she sustains a leg injury en route to university entrance exams, mirroring an earlier incident involving Nariyuki. This injury catalyzes mutual confessions of their feelings, resulting in them becoming a couple.