The captivating realistic cover of "The Demon King's Sex Slave" features a close-up of a slender man with long, flowing white hair that fades into pink at the ends. His ice-blue eyes are wide with a mix of fear and desperate adoration. He wears a tattered white robe with gold trim and ornate ice-patterned shoulder guards, slightly exposing his chest. A harsh, crimson light casts long shadows across his pale face, highlighting a trickle of blood near his lips. In the background, a looming, muscular man with crimson eyes and demonic tattoos clenches his fist, his face obscured in shadow, suggesting a violent presence. The title, "The Demon King's Sex Slave," is emblazoned in a dark, gothic font, dripping with crimson accents, to emphasize the dark themes within.