Masatora Akutsu is a demon who has been sent to Earth to recruit humans to help in Hell's war against Heaven. He falls in love with Lily Amane, a girl he is hoping to recruit but unfortunately for him she is an angel with the job of hunting demons. She defeats him but rather than killing him she enslaves him; the collar she forces him to wear makes him do whatever she commands. As the series progresses they grow closer to each other; perhaps he will be able to use her to change Heaven.
I thought this was a fun enough series. The sort one enjoys while watching then forgets once one starts watching something new. The plot is decent enough if not the most original and the characters are likeable. The animation is good as are the character designs. There is some decent action, particularly when Lily's brother shows up. Overall; not a must see but fun enough.
These comments are based on watching the series in Japanese with English subtitles.