Masako Negishi is a junior high school student and one of the best friends of the protagonist, Shuri Komori. She is fourteen years old and serves as the class representative. As the youngest of the Negishi siblings, she shares a close bond with her family, though the series focuses more on her school life. She has long black hair that reaches her waist and gray eyes, and she is notably small in stature.

Masako’s personality is level-headed and intelligent, often acting as the voice of reason among her friends. She possesses a calm and somewhat dark aura, yet her small size and cute appearance soften this impression. She is clever and occasionally uses her intellect to outwit others, revealing a mischievous streak. One of her more unusual habits is striking poses reminiscent of a yakuza, which can appear fierce and intimidating despite her diminutive frame.

Her primary motivation stems from her deep care for Shuri, who is incapable of declining any request. Masako frequently worries about Shuri’s workload and works together with their other close friend, Megumi Nishitori, to try to rein in Shuri’s self-sacrificing tendencies. This protective role defines much of her involvement in the story. She is a supportive and loyal friend, always ready to help when needed.

Throughout the series, Masako remains a stable and grounded presence, with her development centering on her growing ability to balance her concern for Shuri with letting her friend live her own life. Her notable abilities include strong organizational skills as class representative, sharp wit, and a knack for strategic thinking. While she does not possess extraordinary physical traits like Shuri, her intelligence and reliability make her an indispensable member of the group.