Ai Sunakawa is the older sister of Makoto Sunakawa in My Love Story!!. As a first-year student at Sakurasaki University in Nagoya, she is depicted as a young woman with red, shoulder-length hair and brown eyes. Takeo Gouda, who has known her since childhood, affectionately refers to her as Sister.

She is characterized as a caring, reliable, and responsible individual who is particularly protective of her younger brother, Makoto. Beneath her composed and mature exterior, she harbors a long-standing romantic affection for Takeo, which began when she was in the sixth grade. For years, she believed that she was the only girl who could truly appreciate Takeo's unique and admirable qualities, and she assumed he would never find another girlfriend. Consequently, when Takeo begins dating Rinko Yamato, Ai experiences significant heartbreak and initially struggles to accept their new relationship.

Despite her personal pain, her empathetic nature allows her to recognize Rinko's genuine feelings and the sincerity of her worries regarding Takeo. This understanding leads her to set aside her own jealousy and become a supportive figure for the couple, helping to foster their romance. Her internal conflict does not vanish entirely, and her lingering feelings for Takeo are accidentally revealed on one notable occasion when she is easily hypnotized for fun at a drinking party and confesses her true emotions aloud. While this incident encourages Hayato Oda to urge her to confess to Takeo, she ultimately decides against it, resolving to move forward. Over time, she begins to develop new feelings for Oda, indicating her gradual emotional growth and her journey toward finding her own happiness.