 If you liked
Sora no Otoshimono
|
 ...then you might like
Gokukoku no Brynhildr
|
Not-so-ordinary-harem with pretty girls who are not exactly humans.
"Pretty girl is supposed to kill the group but eventually she will join to them" concept.
Sora no Otoshimono is more comedy and Gokukoku is more gore but I like both of them and story is really quite similiar, I'm quite surprised that I'm the first one making this suggestion :)