Dear Door 01 (レジコミ フーシア)

After the loss of his fiancée, police officer Kyungjoon resigned himself to a life of watering his house plants and catching two-bit criminals. But after a police investigation into a mysterious cult goes supernatural, he finds himself face-to-face with “Lord Cain,” a demon king in desperate need of mana in order to survive. Good Kyungjoon’s body serves as a “door” through which Cain can enter Hell and restore his mana. Bad the method of opening that door is… not so safe for work...