TV-Series
Description
Kyouya Onodera arrives at the island school as a transfer student with Nana Hiiragi, maintaining an aloof and guarded exterior that keeps classmates at a distance. His past holds profound tragedy: the ambiguous deaths of his parents forced him into poverty, struggling through multiple jobs to support his chronically ill younger sister, Rin. Feeling burdensome, Rin ultimately tampered with Kyouya's vital journals and vanished, leading him to gradually forget her existence.

Possessing extraordinary observational and deductive abilities, Kyouya analyzes situations and people with sharp precision, skills rivaling Nana Hiiragi's and prompting his early suspicion of her role in the island's dark events. Despite this intellect, he exhibits social awkwardness, openly desiring friendship yet struggling to connect due to an outdated manner of speaking. His broad knowledge stems from interests in retro video games, manga, and voracious reading.

Kyouya's talent is immortality, granting survival from fatal harm, rapid healing, and resistance to toxins or fire. This comes with a severe drawback: progressive amnesia erases memories older than roughly two months, with events beyond two years completely lost. He meticulously maintains journals to combat this memory loss, guarding them fiercely against potential manipulation. His immortality also halts aging and leaves him without a functional sense of smell, requiring notes to track perishables.

On the island, Kyouya's investigation into the mysteries intertwines with his personal quest to rediscover Rin, whose presence lingers only in faint muscle memory. His dynamic with Nana shifts from mutual distrust towards reluctant cooperation, especially after uncovering her true mission and government manipulation. Following a time skip, his agelessness leaves his appearance unchanged, and he adopts a watchman role. His relentless search for Rin eventually reveals her capture and experimentation. Their reunion occurs under dire circumstances, with Rin imprisoned and unable to fully access her own talent.