Nazuna's unnamed mother plans to remarry and relocate, prompting her daughter's distress and escape attempts. Her impending marriage establishes the central conflict, as Nazuna fiercely opposes both the move and the new family structure.

She actively intervenes to halt Nazuna's plans, confronting her daughter first at their home and later at the train station alongside her fiancé. During these encounters, she physically drags Nazuna away while her fiancé restrains Norimichi when he tries to intervene.

Nazuna's dialogue reveals a significant aspect of her mother's past: an extramarital affair that resulted in Nazuna's birth. This history fuels the strained relationship, contextualizing Nazuna's criticism of her mother's character and her own fears of repeating similar choices.

Her narrative function centers on enabling the central conflict through her remarriage plans and her opposition to Nazuna's autonomy.