Ren and Road Nightmare

Nightmare as sent his two 'kids' to Popstar to get rid of some people in his way. Ren is the cold, serious, and quiet one. His sister, Road, is the cheerful, outgoing, and insane one. Quite a pair, the two, unbeatable, for now. Until they come to Popstar and meet their match. Emotions. Something a Demon Beast is not accustom too nor knows how to control. Can they complete the task?