Azusa Noyama earned the nickname "Azuki-chan" when classmate Ken Takayanagi misread her name on their first day of first grade. She initially disliked it but embraced the name in fifth grade after transfer student Yūnosuke Ogasawara expressed fondness for it, sparking her immediate romantic feelings. She lives in a Tokyo apartment with her mother Keiko, father Tadashi—skilled in voice mimicry and household repairs—and younger brother Daizu, who often annoys her by revealing private matters and navigates his own romantic subplots. Her paternal grandfather, former police officer Gōzō Noyama, initially opposed her relationship with Yūnosuke but accepted it after a personal realization influenced by memories of his late wife.

Azuki displays typical pre-teen enthusiasm and occasional jealousy, particularly when Yūnosuke interacts with other girls. She sometimes leaps to dramatic conclusions, like fearing pregnancy after sharing a kiss with Yūnosuke following an incident where older students bullied him. Her close-knit friend group includes Kaoru Nishino, Midori "Jidama" Kodama (a tomboy in coveralls who avoids romance but briefly crushed on a married police officer after a robbery), and Tomomi "Tomo/Tomoko" Takahashi. They formed the "Club of Unreturned Love" to discuss romantic challenges: Kaoru pines for Ken, Tomomi pursues Yūnosuke's friend Makoto Sakaguchi, and Jidama navigates her fleeting crush.

Azuki's romantic focus centers on Yūnosuke, whom she diligently pursues despite competition from affluent classmate Yōko Sakakibara. Key developments include sharing a diary with Yūnosuke to solidify their relationship and navigating misunderstandings, such as jealousy toward a new music teacher. She demonstrates growing emotional maturity by moving past minor jealousies and maintaining their bond amid external pressures. Her grandfather’s eventual acceptance marks significant familial acknowledgment. Her arc depicts gradual maturation while retaining earnestness and affection for Yūnosuke, with no progression beyond elementary school depicted.