The Visitor from Hell

In order to achieve a certain goal, the male lord had traded with the demon to become a devil's messenger. Originally, they were trying to use their own abilities to do something useful to Earth, but who would have thought that they would turn into monsters that were devoured by the Hell Demons. After the backlash, his evil slowly surfaced.
At the end of the story, justice and evil, love and evil, who is the master of them? "