Hijiri Kirishima is the older sister of Kano Kirishima and operates the Kirishima Clinic as the town's doctor. Following the death of their parents, she assumed the role of Kano's guardian and sole remaining family member. Her motivation to become a doctor was directly inspired by her sister's condition, as she believed that pursuing a medical career would allow her to find a way to cure Kano's mysterious illness.

In terms of personality, Hijiri is generally depicted as calm and composed, but she possesses a strict and hardworking demeanor. She has a notable aggressive streak, often threatening or chasing the protagonist Yukito Kunisaki with a scalpel, which she carries with her constantly. This behavior is partly practical, as she keeps the scalpel on her person to prevent her sister from accessing it. Her wardrobe is recognizable by her usual outfit, which includes a gown worn over a T-shirt emblazoned with the word "Tongcheongak" or "通天閣". She is intensely protective of Kano, bordering on excessive, and she can become frantic or extreme in her actions when responding to anything that affects her sister.

Within the story, Hijiri serves as a key supporting character in Kano Kirishima's narrative arc. Her role becomes active when she encounters Yukito performing his puppet show outside her clinic. She allows him to continue performing there on the condition that he also works at her clinic, making her his employer and integrating him into their daily lives. Her deeper involvement is revealed when she explains the origin of the yellow bandana tied around Kano's wrist. She discloses that the bandana is not a magical charm, but a psychological safeguard she devised after witnessing a young Kano attempt to harm herself with a knife. By tying the bandana and telling Kano it would grant magic powers if kept until adulthood, she hoped it would serve as a visual anchor to snap her sister out of her dissociative episodes.

Hijiri's most significant relationship is with her sister Kano, whom she cares for with total devotion. Her relationship with Yukito evolves as the story progresses. Initially viewing him as a drifter to be bossed around, she gradually develops a genuine, if subtly expressed, affection for him. This is demonstrated through her actions, such as using a government stipend to pay him to stay, effectively halting his journey and offering him a place as part of their unconventional family unit. Her development is largely defined by this growing acceptance of others into her previously insular life with Kano, showing a capacity for building new familial bonds.

Hijiri possesses the skills of a trained physician, and although her career is relatively short, her abilities as a doctor are considered competent. Beyond her medical expertise, she has a distinctive habit of wielding a scalpel not only as a tool but also for intimidation and even as a substitute for a kitchen knife. She is also notably physical, sometimes engaging in playful violence, and has a particular interest in the idea of dissecting Yukito, given the proper facilities.