Akane Aki, also called Anna internationally, transfers to Seirin High and joins the school's basketball team as assistant coach. Her athletic experience includes middle school table tennis. When the protagonist moves into her family home after his parents relocate abroad, she develops a significant connection with him. Initially viewing him as eccentric, her feelings deepen into genuine affection and romantic interest, accompanied by noticeable jealousy when he interacts with other girls.

She shares a notable bond with her pet dog; the dog harbors romantic feelings for her and actively schemes against the protagonist as a rival for her affection. Akane remains unaware of the dog's human-like thoughts or its affection. Her personality blends kindness, patience, and emotional supportiveness, especially towards the protagonist, often acting as his grounding influence during chaos while maintaining a wholesome, sincere demeanor.

A key subplot involves her past relationship with Daiba, an ex-boyfriend from a rival basketball team. His violent tendencies caused their breakup, and his subsequent attempts to undermine the protagonist while trying to regain her affection fuel ongoing conflict. Beyond basketball, Akane navigates school life, interpersonal relationships, and occasional participation in other sports. Her dynamic with the female coach, characterized by contrasting personalities, fuels team interactions and comedic situations. Mutual romantic feelings between her and the protagonist are confirmed by the series' conclusion.

Her dog periodically breaks the fourth wall to explain sports rules during matches, though Akane cannot hear this within the story. Her family provides a stable environment for both her and the protagonist following his transition into their household.