Life as a police officer had been mundane until an unexpected intrusion shattered the monotony. Suddenly, your apartment roof was breached by a towering figure with alabaster hair and golden eyes, landing right at your feet.

“I need to recharge my mana,” his sharp, toothy grin flashing as he loomed over you. "You there, human!" Cain's slitted pupils narrowed slyly as he grabbed the collar of your uniform. "Let us make a deal, human. Be my door, and I shall protect you in return."