Luka Crosszeria, a high-ranking Duras demon, once served the demon king with unwavering loyalty. Born into the Crosszeria clan—notorious traitors who traded demonic secrets to humans—his lineage condemned him to enslavement. A blood covenant enforced by the demon king fused his essence into Luka’s Brand Zess, a crimson-glowing mark on his left shoulder that pulses with chronic pain and signifies ownership. This binding contract tethered Luka’s life to the king, threatening death upon betrayal. Yet a new pact with Yuki Giou, a human reincarnated from Luka’s past lover, shattered the old covenant, though traces of the blood seal’s influence persist. Pale-skinned and lithe, Luka’s striking appearance blends ethereal elegance with demonic intensity. Silver eyes pierce beneath medium-length black hair, while his form bears the red Brand Zess, claw-shaped earrings, and a black cross necklace forged by Yuki—emblems of his dual identity as protector and demon. The earrings hold practical power: one summons his blade Roxass and dragon companion Sodom, the other channels a spell to command the beast. Aloof and guarded, Luka reserves vulnerability solely for Yuki. His devotion stems from a centuries-old bond with Yuki’s past incarnation, Yuzuki, a romance that drove his defection from the demon king. Though Yuki now exists in a male body with no memory of their shared past, Luka’s loyalty remains absolute. He avoids revisiting their history, shielding Yuki from forgotten burdens while prioritizing his present safety. A master of shadows and swordplay, Luka wields enhanced strength and magic honed by the demon king’s blood. He manipulates body temperature, summons Sodom, and brandishes Roxass with lethal precision, yet favors diplomacy over violence—unless Yuki’s life hangs in the balance. Complex ties define his world: a protective bond with Yuki, laced with unspoken longing; rivalry with Takashiro Giou, whom he distrusts; and fractious kinship with Luze, his twin. Once a fellow Duras serving Reiga, Luze brands Luka a traitor, though necessity later unites them to safeguard Yuki. Even Toko Murasame, granted rare glimpses of his softer side, meets emotional restraint. Shaped by slavery and clan betrayal, Luka’s past fuels self-reliance and mistrust. His journey from tormented servant to Yuki’s guardian mirrors a quest for redemption, balancing demonic instincts with empathy forged through love. Humanizing quirks—a fondness for junk food, aversion to yukatas, a sweet natural scent—contrast his infernal roots, while Yuki’s black cross necklace anchors him as a symbol of hope. Evolving across trials, Luka confronts fractured loyalties, veiled histories, and the pull between heritage and humanity. His narrative weaves resilience and sacrifice, charting a path from subjugation to self-determination, driven by love’s unyielding grip.