Yuzuha Usagi is a highly skilled mountain climber and athlete thrust into the Borderland survival games, where her physical prowess in Spades-type challenges—agility, strength, and endurance honed through climbing—proves vital. Born to mountaineer Shigenori Usagi, she joined expeditions young, seeking refuge in nature from social difficulties. Her father’s reputation collapsed after accusations he faked an oxygen-less Everest ascent. In the manga, these claims drove him to suicide, his final words being "I have never lied to the mountains." The Netflix adaptation depicts his disappearance after telling her he was "going to the mountains." Both events left her isolated, grappling with unresolved grief. She entered the Borderland during a meteor shower, her body uniquely avoiding temporary marionette transformation. Initially, Usagi survives alone, believing attachments hinder survival. She clears games like the Four of Spades solo, trapping small animals for sustenance. Her first encounter with Ryohei Arisu occurs during the Five of Spades game, where she scales apartment balconies vertically. Reluctantly, she cooperates with his plan to share "Horse Head" intel, surprising observers like Shuntaro Chishiya. After clearing the game, she rejects Arisu’s team-up offer, warning of future betrayals. Her resolve wavers after witnessing Arisu’s despair following his friends’ deaths in the Seven of Hearts game. She rescues him, shelters him at her camp, and teaches wilderness skills—hunting and knife handling. They grow closer while seeking the "Beach" organization for Borderland answers. At the Beach, she faces threats, including an attempted rape by Suguru Niragi interrupted by the Ten of Hearts game announcement. Later falsely accused as the "Witch," she nearly dies at militants’ hands before escaping to find Arisu. Usagi’s loyalty to Arisu deepens, though she doubts returning to the real world. During the Interval, she hesitates when he insists they leave together, fearing she cannot forgive the world that condemned her father, straining their bond. In the King of Clubs game, she volunteers for a high-risk role, recognizing her physical abilities have heightened under duress. An arm injury occurs, stabilized with a triangular bandage. After ally Kodai Tatta’s death, she supports Arisu’s choice to abstain from games temporarily. Their relationship turns romantic during the Fourth and Fifth Days of Exhibitions, sharing intimate moments in a hot spring at the former Seven of Spades arena. During final confrontations, she saves Arisu in the Queen of Hearts game by slitting her wrist to shatter Mira Kano’s psychological trap, enabling his victory. Both reject permanent Borderland residence and return to reality. Post-return, Usagi remembers nothing of the Borderland but meets Arisu in a hospital. He asks her out, and they build a relationship. Eight years later, they marry, her name becoming Yuzuha Arisu. Pregnant, she goes into labor while Arisu is away. Her childbirth phone call coincides with his near-fatal accident, fueling his will to survive a second Borderland ordeal. Usagi evolves from a detached survivor to a fiercely protective partner. She retains pragmatic, analytical problem-solving but embraces trust and teamwork, especially with Arisu. Her physical mastery parallels emotional resilience—confronting trauma, defending allies, and strategizing under pressure defines her journey.