A reaper is a low class god . They exist in a different dimension than those of humans and deemed unnecessary they have not any foolish senses that cause anguish. But one of them is different . He wants to be a human but to do so he has to guide 10 000 000 people to hell

“Things that should not be touched by humans somehow find their way into this world. That’s why you should never, ever touch anything that is foreign.”
Follow the adventures of March, a Syste Behard, who hunts ils– evil creatures that lurk in fascinating objects.
Among the quiet villages and towns of 18th century Europe, demons known as the Ill hide within the most beautiful works of art, sparked to life by the torment of their creators. Attracted by their jewel-like allure, the unwary find themselves possessed by the Ill and driven to horrific acts of violence. Only the hunters of the Ciste Vihad can dispel the Ill.March is one such hunter, tracking the Ill from town to town to find the antiques that contain the demons before they can possess anyone. If the worst has come to pass, March's full powers are unleashed to battle the fiendish Ill. Born of tragedy, the artifacts all have their own tales to tell, as do each of their victims. But March's story may be the most tragic of all.
(Source: etc)

The series begins as a guest visits a temple where Myo-Un and Ryu-Sang are living along with many other orphan children. This guest turns out to be an assassin who came to kill a certain someone who is the last child of a powerful family in Su country. The assassin's employer, who remains anonymous, wants to clean up every root of possible problems.
The assassin calls for reinforcements and attacks the lady of the temple, revealing that the lady of the temple is also another last descendent of another powerful family that was drawn out of Su country. Myo-Un, Ryu-Sang, and others are forced to flee the temple.
Thus, Myo-Un & Ryu-Sang's journey begins, and the assassin is still after them.
Readers, at this point, are challenged to figure out who might be "the last child". It's either Myo-Un or Ryu-Sang, and even at volume 5 (which is the latest volume at the time of this article), readers will still not likely know who is "the last child" that the assassin is after.
There are three major protagonists in this manhwa. As you may have guessed, the two are Myo-Un and Ryu-Sang. The third is the assassin whose name is Harim.
(source: JanimeS)