Demon Immortal Shadow Destroying Art

Everyone in the world has become an immortal, but I alone have become a demon. In order to take revenge, a young man wants to fall into the devil's path and practice demonic skills. I want to ask the sky, what is a demon and what is an immortal? Immortals and demons are innocent in nature, but in a single thought, the heaven and earth are not working, and they act against heaven.