One Thought Turned into a Devil and He Became a Devil

One day he actually learned that his master was his enemy, so he became a demon in a thought Where is this? Some four-legged monster? After figuring it out for a long time, this place turned out to be a parallel world, and he actually found the intersection of two parallel worlds. He travels back and forth between modern society and his ancient past. Two worlds, the same identity, two different people, is the world in chaos? This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.