The entirety of "The Evillious Chronicles".
And the song in which an angel (Rin) falls in love with a human girl (Miku), so Rin makes a contract with the devil so she can become a human man (Len) and have a relationship with Miku, which ends up successful. Then another angel, Kaito, becomes jealous of Miku because Kaito was in love with Rin, so Kaito kills Miku. Rin sacrifices her own life so Miku can live again, the end. I forgot the title. Shame too, because the tune is stuck in my head. I think it's called "Forbidden Secret ~Black Vow~".