I'm in the Wasteland, and I've Traveled Through Time and Become My Own Contracted Beast.

Su Mo never thought that he would become a non-human being with a white tail, let alone that he would be trapped in the land of illusion, the purgatory of contestants. Of course, something unexpected happened in another place in the same time and space. Su Mo found that he was reborn and transformed with some memories of his previous life. At the same time, he also had an annoying younger brother, living a relatively high-quality life in the wasteland world... (The introduction is weak, and so is the text...)