Gyeong Joon a police officer. One day Cain who is from hell realm not from human realm like Gyeong Joon came to human realm to fight satan ithink he needed smtg. Gyeong Joon became Cain's door. Cain can go to hell reallm when his door opens by that when he cums. Later Cain found his expressions interesting n seductive so he did sex to go to hell. They keep doing this a lot (sex) and none of them realized their feelingd, more like they did eventurlly. Cain is fighting demons who r illigally coming to this world bcs the sigil should have the owners name on it but none of the humans have the sigil. Which is a cause why people in the town/city r dying, getting drained by demons. Luckily Gyeong Joon is diff den others his soul is very strong. Things happen such as jealousy,sadness,lies,protection n many other things. But dis makes them grow stronger in many ways.
Dear Door