Makio Kōdai is a thirty-five-year-old professional novelist and one of the two central figures in the story. She writes under her own name and is known as an author of girls' novels and essays. Her life changes abruptly when her older sister Minori and Minori's husband die in a car accident, leaving their fifteen-year-old daughter Asa Takumi orphaned. Despite having a strained relationship with Minori, who often berated her for being different, Makio impulsively decides to take Asa in after witnessing how the rest of the extended family treats the girl as a burden.

Makio is reserved and strongly dislikes social contact. She is shy around other people and socially awkward, finding ordinary human interaction draining. She is naturally blunt and not very expressive, and her personality clashes with Asa's more friendly and outgoing nature. She also lacks domestic skills and lives in a cluttered apartment filled with books, which reflects her internal world. Her decision to take in Asa is impulsive, and the next day she realizes how unsuitable she is to live with someone, having forgotten her own difficulties with personal interaction.

Her central motivation is not to understand Asa's feelings but to accept them as valid. She tells Asa that they will never truly understand each other because they are separate individuals with different internal languages, framing their cohabitation as akin to living with someone from a foreign country. She affirms Asa's right to feel whatever she feels, even when those emotions conflict with societal norms. This approach respects the boundaries between them rather than forcing a traditional family bond. Her role in the story is thus to provide a space where Asa can grieve and process her complex emotions without pressure or judgment, while also navigating her own reentry into social life after years of isolation.

Makio's most important relationship is with Asa, her niece. Their dynamic is one of mutual adjustment, with Asa often taking on practical household tasks while Makio provides intellectual and emotional support. Another key relationship is with her late sister Minori, whose memory looms over the story. Makio harbors resentment from their difficult childhood, and discovering Minori's old journals forces her to confront a more nuanced view of her sister. She also maintains a relationship with Shingo Kasamachi, her ex-boyfriend and confidant, who offers a mature, post-romantic friendship. Her editor Nana Daigo occasionally intervenes to ensure Makio fulfills her duties as a guardian.

Across the story, Makio develops by gradually opening herself to a life that includes another person. She begins to socialize for the first time in years, and the practical failures of her artist-guardian role become opportunities for growth. The rigid boundaries she erects, symbolized by her description of herself and Asa as different countries, soften as they find ways to coexist without losing their individuality. Her development is not about becoming a perfect guardian but about learning to respect independence while offering protection.

Notable abilities include her skill as a novelist, which gives her a tendency to view life through narrative frameworks. She often makes blunt, insightful observations about people and situations. She is fiercely protective of Asa when the girl is mistreated by relatives, showing a capacity for decisive action despite her usual passivity. Her most prominent trait is her ability to articulate the importance of emotional autonomy, telling Asa that feelings belong only to the person who has them and are not for others to judge or trample on.