Between this world and the next exists a special world. It's a dimension of life phantom in nature yet one very real. Access to it is granted only on certain occasions and the times of admission are brief windows lasting mere seconds. The stay in that world depends on how long the soul braves to stay there, because in all honesty, it is a terrifying country. It is Arco, the other world, the world of the inbetween.

Memories from childhood concerning two certain monsters surface up for Jiho when she receives a letter from the government. She has been selected to join the workforce as a soldier and the thought of wielding arms petrifies her, certain that by taking up arms she would summon the two fiends. Yet she is obliged to do it or else lose her mother's love. When she takes up the sword she learns that Death and Decay are two very real things. Her world that was devoid of the knowledge of these two na

After the death of his wife, Nayeon, Sungkyu's life becomes hell. 2 years after her death he attempts suiciding, but fails and find himself face to face with Woohyun, a former classmate whose prank introduced Sungkyu to Nayeon in the first place. Soon enough the two find themselves in a war against fallen angels, where Sungkyu takes on the form of a monster in order to seal them in hell. At the end, despite beginning his life anew with Mina (former classmate as well), Sungkyu is forced to dea