Thousands of Years Ago, I Was Also Loved by Someone

He has walked the world for thousands of years to atone for the catastrophe he caused. Why did the mysterious girl enter the academy? What is the identity of a frail and sickly boy? What secrets does an ancient tree hide? Can the entanglement of love be consummated? Chaos first opened, the world was born, and then demons came to the world. A guardian used himself to suppress these demons, but he did not want to be released by a divine bird. Someone has to bear the sins, and someone has to recover these evil things... Thousands of years later, the original peaceful life of the ancient country was shattered by the birth of several children. A battle between humans and demons begins...