Giusy Young, the localized Italian name for Akiko Hoshi, is the elder sister of protagonist Hyūma Hoshi and daughter of Ittetsu Hoshi. Following their mother Harue's death, she steps into a maternal role within the household, providing emotional support and stability against the backdrop of their father's harsh training methods and the family's impoverished life. Her protective instincts toward Hyūma frequently manifest, sometimes leading to direct confrontations with Ittetsu over his treatment of her brother. Significant conflicts include her departure from the household after a major disagreement concerning Hyūma's well-being, and later, she directly blames Ittetsu when Hyūma suffers a severe career-threatening arm injury, accusing their father's methods of contributing to the damage.
Her interactions extend beyond the family. She receives flowers from Mitsuru Hanagata, Hyūma's rival, an act prompting speculation about romantic interest from Hyūma's perspective, though the context remains ambiguous. She maintains a supportive relationship with Mitsuru, who intervenes during her emotional confrontation with Ittetsu over Hyūma's injury, calming her and offering assistance.
The character's background includes living with her brother and father in impoverished conditions, specifically an old post-war nagaya complex. Her mother's death profoundly impacts the family, fueling Ittetsu's bitterness and compelling Giusy/Akiko to assume caregiving duties at a young age.