Inspired by the fic Ranmazoku.  Ran is a demon that has been given the task of helping his demonic lord to conquer the Earth.  He and his fellow demons are to unravel the barrier that prevents strong demons from entering the Earth's reality.  Ran infiltrates the Earth by taking the place of a child killed by starving cats.  While Ran is one of the weakest of demons, he was chosen because he always finishes what he starts...