Hagumi Hanamoto, often called Hagu by those close to her, is a central figure in her story as an immensely gifted young artist. At the beginning of the narrative, she is eighteen years old, though her small stature and childlike demeanor often cause others to perceive her as much younger. She was raised in a very sheltered and isolated environment in Azumino city, Nagano Prefecture, primarily by her irritable grandmother. With few other pursuits, she spent her childhood drawing and painting, often focusing on the unchanging view from her porch as it varied with the seasons. Her sociability is notably low as a result of this upbringing, and she is prone to stress-induced physical ailments, such as fevers and illnesses, when faced with overwhelming situations.

Hagu's personality is defined by her profound shyness and a gentle, kind-hearted nature. She is easily frightened and becomes very nervous when interacting with people she does not know well, which leads some of her peers to think she is strange. Beneath her quiet exterior lies a deep sensitivity and a pure, almost naive way of viewing the world, a quality that others often find captivating and which is distinctly reflected in her artwork. She is self-conscious about her childlike appearance and has been known to cry out of envy upon seeing the more developed figures of her friends.

Her primary motivation is her art; creating is not just a hobby but an essential part of her being. She is driven by an internal creative passion, and her life largely revolves around her need to draw, paint, and sculpt. This immense talent, however, also becomes a source of great stress. Professional artists and gallery directors constantly urge her to submit her work to exhibitions, a pressure she finds daunting and which contributes to her physical fragility. She is deeply troubled by the thought that her needs and her frailty make her a burden to her guardian, Shuji Hanamoto. Her journey often involves navigating the tension between her desire to create freely and the external demands placed upon her by the art world.

In the story, Hagu acts as a catalyst who profoundly affects the lives of those around her. She is introduced to the main group of friends by Shuji Hanamoto, her father's cousin and a professor at the Tokyo art college they all attend. Her arrival creates a significant emotional shift, as two of the male leads, Yuta Takemoto and Shinobu Morita, fall in love with her at first sight. While both express their feelings differently—Takemoto with a gentle, hesitant affection and Morita in odd, mischievous, and sometimes overwhelming ways—Hagu remains largely unaware of the depth of their romantic interest for a significant portion of the story, viewing them primarily as important friends.

Her key relationships define her world. The most crucial is with Shuji Hanamoto, whom she fondly calls Shu-chan. He is her guardian, protector, and a soothing presence, acting as a calming rain in her life. She relies on him immensely, and their bond is a central source of stability for her. She also forms a very close friendship with Ayumi Yamada, a skilled potter whom Hagu calls Ayu. When Shuji leaves for a research trip, Hagu lives with Yamada, and they become confidants and like family to one another. Her relationships with Takemoto and Morita are more complex, forming the emotional core of much of the narrative. Takemoto's heartfelt confession of love eventually leads her to avoid him out of confusion, though she ultimately proves she considers him a precious friend. Her connection with Morita is unique, as his own artistic genius allows him to understand and inspire her on a level others cannot, and she eventually accepts his confession of love.

Throughout the narrative, Hagu experiences significant development. Initially a deeply isolated and timid girl, she gradually warms up to her new friends, coming to see Takemoto, Morita, Mayama, and Yamada as a surrogate family. She finds her own strength and voice, ultimately making a profound choice about her future. It is observed that there are people who pursue love and those who choose passion, and Hagu is described as the second type. In the end, despite her romantic feelings for Morita, she makes the decision to return to Shuji to focus on her recovery and her art, demonstrating that her creative calling is the defining force in her life. Her most notable ability is her supreme artistic talent, which is esteemed by all who witness her work. She possesses a unique visionary quality, allowing her to create pieces that are not only technically masterful but also deeply expressive, effectively making her thoughts and emotions visible on canvas or in her sculptures. This ability to capture and convey a unique perspective of the world is what sets her apart as a true artistic prodigy.