Nagisa Hazuki, a cheerful and energetic Leo born August 1, thrives on instinct and candid expression. The youngest of four siblings, his three older sisters often dressed him in girls’ clothing—a playful tradition extending into high school. This upbringing fueled his admiration for Haruka Nanase, who once offered Nagisa a swimsuit after his sisters swapped his own, cementing his resolve to swim alongside Haruka. During elementary school, Nagisa trained alone after Haruka and Makoto Tachibana advanced to junior high. Inspired by Rin Matsuoka’s introduction to butterfly stroke techniques, he aspired to master multiple swimming styles. Yet early relay races with Haruka, Makoto, and Rin left him wary of solo competitions. Determined to reconnect with Haruka and Makoto, Nagisa enrolled at Iwatobi High and spearheaded the revival of its swim club. His unconventional recruitment of Rei Ryugazaki—drawn to Rei’s pole-vaulting grace and their shared gender-neutral names—showcased his inventive problem-solving. As club treasurer, Nagisa mentored Rei through initial struggles, teaching him to swim. Academic pressure from his parents clashed with his athletic dedication, leading to slipping grades and a brief departure from home. Encouraged by Rei, Nagisa confronted his family, voicing his passion for swimming to secure their tentative support. Specializing in breaststroke, Nagisa’s technique features a post-turn speed surge and an illusion of elongated arm reach. His enthusiasm for horror stories and thrill rides mirrors his competitive resilience. Academically, he excels in history but grapples with mathematics. Post-graduation, Nagisa joined Naribusawa University’s swim club, mentoring kouhai Kaede Kinjo. His habit of assigning affectionate nicknames like "Haru-chan" and "Rei-chan" underscores his role as a social bridge, balancing personal drive with evolving obligations amid familial and academic challenges.