Oz Mare is a middle-aged, bald agent of Dorothea, the organization combating illicit fairy operations, clad in its standard uniform. As part of Dorothea’s elite First Unit, he executes missions ranging from combat to surveilling fairy-related crimes, aided by a fairy that takes the form of a bull, though its abilities remain undocumented.

During a high-stakes operation escorting a fairy weapon for Duke Diese, Oz’s team is ambushed aboard a train by Beevee Liscar’s forces. Confronting Beevee directly with his fairy, Oz is overpowered and left critically wounded. When Sophie, an assailant, targets fellow agent Marlya Noel, Oz throws himself in front of her, shielding her with his body. Bullets tear through his back, yet he persists in guarding her until his legs buckle. Beevee, deeming further survival cruel, delivers a fatal strike—a gesture he frames as mercy. Oz dies with a faint smile, his body still draped over Marlya, as Dorothea agents converge around him.

Before this mission, Oz is established as a supportive colleague, joining teammates at gatherings like Marlya’s post-mission welcome party and openly praising her sharpshooting skills. His actions and interactions reflect a camaraderie-driven nature, prioritizing team safety above all.

His death accentuates themes of sacrifice and war’s lingering scars, cementing his legacy as a protector. Though brief appearances limit exploration of his background, his sacrifice deeply affects Marlya, intensifying her belief in a personal curse forged by recurrent loss.