DISCOVERY. BETRAYAL. SACRIFICE. It’s a literal Hell on Earth as demons use doors--unwitting human portals--to wreak havoc on the mortal realm. Kyungjoon has now eased into the role of door to the Demon King Cain, though he's at first reluctant to admit that he’s developed feelings for the king. Cain also has grown fond of the human. But their relationship might prove short-lived, as an angel’s weapon has wounded Cain and time is running out for him. The only way to save the demon is for the weapon’s shard to be removed, and the only one who can remove it is a skilled doctor-demon who's currently on the run. Unknown to Cain, someone from his own camp is preventing the doctor from being found. Besides, to cure Cain, a sacrifice must be made... and it’s a sacrifice that might prove too great to give. Series Overview: After a devastating personal loss, Kyungjoon wants nothing more than to drown his grief in the silence and safety of his houseplants. But Kyungjoon is also a cop, and it’s a cop’s job to go after criminals. One day, hot pursuit of a suspect leads to Kyungjoon discovering signs of cult activity. Soon, the policeman is caught up in the machinations of monsters and demons, the worst of which is the demon king, Lord Cain, whose survival in this world depends on mana that can only be accessed through a "door. To open Cain’s door residing inside Kyungjoon, these two will have to get up close and very personal! For Mature Readers.