Giusy Young, known as Akiko Hoshi in Japanese, serves as the older sister of protagonist Hyuuma Hoshi. Following their mother Harue's death, she assumes maternal responsibilities within the impoverished Hoshi household, frequently opposing their father Ittetsu over his harsh baseball training methods for Hyuuma. She openly confronts Ittetsu about the physical and emotional toll on her brother, leaving home after a major argument concerning Hyuuma's welfare and later blaming Ittetsu for contributing to Hyuuma's career-threatening arm injury.

Her protective nature and consistent emotional support establish her as a stabilizing presence for Hyuuma, who holds deep affection for her. Her character intersects with the series' baseball narrative through her relationship with Mitsuru Hanagata, Hyuuma's rival and friend. Mitsuru shows concern for her well-being, intervening during family conflicts like calming her distress over Hyuuma's injury. Their relationship evolves into marriage, making Mitsuru Hyuuma's brother-in-law.

Akiko demonstrates assertiveness beyond family disputes, confronting delinquents threatening Chiyo Samon and intervening in dangerous situations involving Kyouko. Flashbacks depicting her parents' relationship reveal Harue as a gentle counterpart to the brooding Ittetsu, whose depression and alcoholism intensified after Harue's death.