Protect the Demonic Four High Emperors

He was once a demon king who was determined to kill all demons. Wherever his iron hoof came, the demons would slay him. Until he went to the Ten Thousand Demons Hall and faced the fox demon master who had saved his life and taught him swordsmanship. "You have finally become my proudest and most painful work." She chuckled and fell under his sword. At this moment, his sword skills were perfect, but his heart was broken. It turns out that all the monsters he killed were monsters that had bullied him and were his enemies; and the last one was the only monster in the world who loved him. Thousands of years later, the Demon King proclaimed himself in an ordinary mountain forest, cleaning and worshiping a lonely tomb every day. Until a familiar figure with unfamiliar eyes appeared in front of him again carrying a food box... The reincarnation of cause and effect, the grievances cut off with one sword, may be the beginning of a new story.