Hiyori Toono, a central figure in Free!'s third season and related media, experienced a lonely childhood marked by his parents' frequent absences, fostering a reserved nature. His isolation eased when a girl named Tomo approached him in a sandbox, offering his first meaningful connection. A pivotal shift came later at a swimming club where Ikuya Kirishima invited him to swim, forging a deep and lasting friendship that alleviated his loneliness and sparked genuine happiness. After his family moved to the United States, Hiyori reunited with Ikuya in high school. Though Ikuya initially didn't recognize him, they reconnected. Hiyori intervened when Ikuya nearly drowned during practice, reinforcing his protective instincts. Aware of Ikuya's fragile health and tendency to overexert, Ikuya's older brother Natsuya Kirishima entrusted Hiyori with Ikuya's well-being before pursuing his professional swimming career. Hiyori accepted this responsibility earnestly, consistently prioritizing Ikuya's safety and emotional stability. Outwardly, Hiyori presents as gentle, polite, and sociable, often wearing a calm smile. He pursues diverse hobbies like reading, frequenting cafes, enjoying egg-based dishes and coffee, listening to rock music, and outdoor activities such as basketball or camping. Beneath this affable exterior lies a deeply protective and occasionally jealous nature, particularly concerning Ikuya. This manifests as competitiveness and sharpness towards those he perceives as threats to Ikuya's focus or emotional state, notably Haruka Nanase and Ikuya's former teammates from Iwatobi Middle School. Hiyori initially viewed these teammates negatively, labeling them "weaklings" and believing they hindered Ikuya's potential as a world-class swimmer. He actively prevented their interactions, confronting Haruka with harsh critiques about his influence. His protectiveness stemmed from multiple motivations: a genuine fear of Ikuya relapsing into self-destructive overtraining, anxiety about being replaced in their friendship, and insecurity regarding his own relevance to Ikuya's swimming journey. These fears, compounded by his history of loneliness, fueled his resistance to Ikuya reconnecting with Haruka. His image animal, the polar bear, symbolizes his outwardly calm yet internally resilient nature. A skilled backstroke swimmer, Hiyori is a member of the Shimo-Roh Academy University swim club alongside Ikuya. He initially opposed Ikuya joining relay teams, believing individual races best showcased Ikuya's strength. A pivotal moment occurred when he raced Makoto Tachibana—a backstroke specialist substituting for Haruka—to uphold his ban on Ikuya's former friends. Though Hiyori won, the reconciliation between Ikuya and his past teammates gradually softened his stance. Ikuya's acknowledgment of their friendship and request to swim together in a relay prompted Hiyori to reconsider his rigidity. His development culminates at the All-Japan Invitational, where Ikuya reconciles with Natsuya. Witnessing Ikuya's growth and restored family bonds, alongside Natsuya's apology for overburdening him, allows Hiyori to relinquish his excessive protectiveness. He becomes accepting of Ikuya's friendships with Haruka and others, participating alongside them, signifying his transition from a solitary guardian to someone trusting in Ikuya's autonomy and supportive network.