If you liked
Ao no Exorcist
|
...then you might like
Hataraku Maou-sama!
|
Both are about young boys (who are demons/have demonic powers) who are also heroes. Both shows are serious at some points, and have comic relief at other points.
If you liked
Nabari no Ou
|
...then you might like
Kuroshitsuji
|
Both shows are about young teen boys who are being protected by an adult male. The demeanor of both main characters is similar. They are even voiced by the same voice actor!
If you liked
Kuroshitsuji
|
...then you might like
Inu x Boku SS
|
Both have Master-Servant relationships. The "masters" are young teens, and the "servants" are adult males. The servants are super strong and good at everything. There is also a bit of comedy mixed in with the seriousness of both shows.
If you liked
Blood+
|
...then you might like
Kuroshitsuji
|
I recommend Blood Plus to anyone who likes Black Butler because both shows are very dark. There is a similar relationship between main characters in both shows: master and servant. Also, there is a supernatural element to both shows.