It is a warm and sad, desperate but strong story; it is also a story that is close to life and breathes with us. The story about the Deer King: when a herd of flying deer is attacked, only one deer will jump out and sacrifice himself to save his companion's life-because it was born that way. The meaning of some lives is to live for death. Van en, after the death of his wife and children, in order to rightly go to another world to gather with his family and join the death squad "single horn", he survived in a battle of total annihilation and became a slave imprisoned in an underground salt mine. One night, a group of mysterious black dogs attacked the salt mine, killing everyone, but he, who was bent on death, brushed past death again. After escaping from the mine, he found the baby girl Yuna, who was hidden by her mother and survived, and the two have depended on each other ever since. However, how can a person who has long abandoned himself and has no attachment to the world protect a newborn life? Hesar, a talented physician, is secretly known as the "son of the Devil God" because his knowledge of research is not allowed in the mainstream. But he always believes that as long as he does not give up, a solution can be found for even thorny diseases. Hesar was ordered to investigate the salt mine incident and learned that the escaped slaves might have the key to the mystery.