Hameln the Violinist as you might have guessed is my 2nd favorite anime. it's one day going to replace Slayers (maybe)
I love this series. Though I only have episode 1-4. Hameln's personnality is different from the episodes , the movie and the manga.
Hameln the violinist's story is about a race of evil beings (The mazoku) doing random evil things. I'm not sure about the plot of the manga but you may check in my story section