Akari Kawamoto is the eldest of the three Kawamoto sisters and serves as the de facto head of their household. Following the death of her mother and the absence of her father, she assumes the primary responsibility for raising her younger sisters, Hinata and Momo, while living with their grandfather. To support the family financially, she works during the day at her grandfather's traditional Japanese confectionery shop, Mikazuki-do, and works as a hostess several nights a week at her aunt's bar in the Ginza district, a job that has earned her a reputation as a renowned beauty among the clientele. She has expressed a desire to one day take over the family confectionery business.

In terms of personality, Akari is defined by her profound nurturing instinct and warmth. She has a maternal quality that extends beyond her sisters, as she cannot ignore any creature that appears skinny or lost, whether it is a stray cat or a lonely person. This trait is central to her character, as it leads her to take in the story's protagonist, Rei Kiriyama, after finding him collapsed on the street, and she continually invites him into her home to "make him fluffy" and provide the familial warmth he lacks. She is an excellent cook and is often dismayed by Rei's unhealthy, solitary lifestyle. While she usually maintains a composed and cheerful demeanor for the sake of her family, she is not without her own vulnerabilities and can be deeply shaken during times of intense family stress, such as when her sister Hinata becomes the target of bullying.

Akari's motivations are almost entirely selfless and rooted in the protection and preservation of her family. A key driver for her behavior is a promise made to her late mother. In an effort to provide her younger sisters with a sense of their mother's presence, she adopted her mannerisms and style of speech, a decision that inadvertently made her seem older and more domestic than her actual age. Her primary goal is to maintain a stable and loving home, and she serves as the emotional anchor for her sisters and for Rei.

Within the story, Akari plays a crucial role as a symbol of unconditional kindness and stability. Her home in Sangatsumachi (March Town) is presented as a stark contrast to Rei's isolated existence, representing a haven of warmth and light. Her relationship with Rei is central to the narrative; she is the first person to offer him a place where he belongs, acting as a surrogate older sister and maternal figure without any expectation in return. Her key relationships are with her sisters, Hinata and Momo, whom she protects and cares for, and with her grandfather and aunt, who help support the family. She also has a unique fondness for Rei's rival, Nikaidou, whose large build she found mesmerizing when they first met.

Throughout the series, Akari shows subtle but significant development. She initially presents a flawless, perfectly composed exterior, but as the story progresses, she is shown to have moments of genuine distress and sadness, revealing the weight of the responsibility she carries. Her resilience is tested, particularly when confronted by her estranged father, whom she tries to welcome peacefully despite her own buried pain in an effort to keep the family together. While she is mature and self-sufficient, her practical abilities have limits; although she manages the household finances well, her understanding of portion control is notably poor, often leading her and Hinata to overeat and regret it later. She is also shown to have gained weight as the series continues, a fact commented on by her aunt. Her most notable ability is her profound capacity for empathy and caregiving, which directly contributes to Rei's emotional healing and growth.