Juana Hazuki is a 13-year-old junior high school student who relocates from Osaka to Tokyo. She moves in with her father, a cameraman recently returned from Peru, and her adopted younger brother, Sunny. Her mother abandoned the family during her early childhood, leading her father to conceal this by claiming the mother had died. Juana remains unaware her mother is actually Kanako Tajima, a famous volleyball commentator and former champion player, until later revelations. This discovery causes emotional turmoil, prompting a temporary departure from volleyball before reconciliation occurs. Sunny displays strong attachment, often following her to school and volleyball activities, viewing her as a Cool Big Sister despite occasional harsh treatment in their early interactions.

Juana demonstrates exceptional athleticism, particularly in jumping ability, and passionately pursues volleyball with the goal of joining Japan's national team for the 1988 Seoul Olympics. Initially portrayed as impulsive and attention-seeking, she exhibits early arrogance and immaturity, including conflicts with teammates and confrontations with her father. Her early volleyball experiences involve struggles with teamwork fundamentals despite raw talent, leading to clashes with the Hikawa Junior High team's captain, Nami Hayase. Their relationship evolves from intense rivalry into a complex friendship, especially after they join opposing professional teams. Training under the abusive coach Daimon involves enduring corporal punishment and harsh methods, shaping her resilience and highlighting the brutal coaching environment.

Her personality shows gradual maturation from a brash, hot-blooded athlete prone to jealousy and stubbornness into a more focused and determined player. She retains traits like a big appetite and occasional overconfidence while becoming more disciplined. Her romantic interest in Sho Takiki, captain of the boys' volleyball team, involves persistent efforts to gain his attention, though this subplot diminishes as volleyball commitments intensify. Key relationships include a friendly rivalry with elite player Eri Takigawa, which transitions into mutual respect and culminates in an Olympic team partnership. Professional growth includes joining the Seven Fighters club, winning championships, and navigating team dynamics with players like Yogina Yokono and Sori Shinoda.

Olympic team formation involves her selection for National Team B. Initial friction with powerhouse teammate Tulia Kaido evolves into camaraderie through competition. Her role culminates in representing Japan internationally. In the sequel New Attacker You!, set years later during the Beijing Olympics, Juana appears as a supporting figure in China's volleyball scene, displaying a calmer, more reserved demeanor compared to her original spirited personality. The narrative focus shifts away from her, with minimal involvement in central conflicts. Adaptation differences exist between media: the manga omits Sunny and depicts Juana's mother as deceased rather than alive, while also streamlining her professional trajectory and romantic subplots. The anime adaptation expands emotional and relational arcs, particularly regarding family revelations and team dynamics.