This is a combined version of the two songs, Rin’s ‘Daughter of Evil’ (悪ノ娘) and it’s alternate side, Len’s ‘Servant of Evil’ (悪の召使い). There’s a story sequel, ‘Message of Regret’ (リグレットメッセージ) by Rin.
Actually, this is not the versions I first saw, but it puts the story together the best, although sometimes the graphics isn’t that great.
The first one I saw for Daughter of Evil is Rin’s “悪ノ娘 PV” with English Lyric, which kind of weirded me out.
As for Servant of Evil, it’s Len’s “悪の召使い” with English Lyric, which had me crying and re-watching it.
For Message of Regret, it’s Rin’s “リグレットメッセージ” with English Lyric Cleaned up, which is a version sequel to the Servant of Evil one. I also cried through this entire video. I can’t find the version prequel, or it would be lovely.
I think the videos themselves should explain the stories well enough, so I won’t touch on them. Go watch them, if you haven’t.