Naja Gref, alternatively romanized as Nadja Gurefu, is a 17-year-old half-human, half-silverwolf Feral enduring prejudice from both humans and full-blooded Ferals. Standing 6'0" tall with an intellectual disposition, he staunchly defends his calculations and viewpoints regardless of accuracy. A recurring attachment to his human mother anchors his background across all portrayals.

Initially aligned with the World Salvation Committee, which upholds the world's order against the World Destruction Committee, he serves as a strategist and tracker. His role leverages analytical skills to mathematically predict enemy movements, often avoiding frontline combat in specific adaptations. He employs throwing weapons—wind and fire wheels—during engagements. Media depictions diverge regarding a special ability: the game and manga grant him a transformative state for powerful attacks, omitted in the anime.

His trajectory shifts dramatically after killing Kyrie at Kyrie’s own request, stemming from despair over destructive powers. This act triggers profound regret and internal conflict, compelling him to abandon the World Salvation Committee and join the protagonists. Motivated by confronting his actions and seeking redemption, this pivot explores loyalty, morality, and the repercussions of hybrid discrimination, with underlying resentment further examined in game and manga narratives.