Tonari, introduced as a 14-year-old girl, is entrusted with the mission to lure Fushi and Pioran to Jananda Island, a prison colony, on Hayase’s orders. Initially framed as an antagonist, her loyalties evolve during her imprisonment alongside Fushi, forging an unexpected bond. As the leader of a group of island youths, she endures devastating losses when most perish in a Nokker assault, trauma that reshapes her resolve. After escaping Jananda, she spends years conditioning her body to become Fushi’s vessel, methodically exposing herself to toxins through her owl companion’s talons to develop immunity—a calculated gambit to strengthen his abilities. Her meticulous planning extends to a journal documenting her insights and experiences, left as a guide for Fushi’s journey. Reemerging decades later as an adult, she aids Fushi during a clash with Hisame, Hayase’s descendant, leveraging her hard-won poison resistance to thwart the latter’s assaults. In their reunion, she implores Fushi to adopt the forms of those they’ve lost, seeking solace in his remembrance of their shared history. Her final act involves confronting the Nokker controlling Hisame, sustaining fatal injuries in the process. Posthumously, Fushi adopts her form to decipher her journal, revealing critical truths about the village doctors and cementing her enduring influence. Once a pawn of manipulation, Tonari’s arc culminates in selfless devotion, her sacrifices emblematic of a life redirected toward shielding others and empowering Fushi’s eternal purpose.