Hakushaku to Yousei, Pandora Hearts Recommendations
Both anime deal with English aristosracy and its morals.
Both have blonde bishounen as the main hero involved in some kind of contract with supernatural heroine. By the way Oz and Edgar have also dark though loyal servants.
And genres are the same: romance, shoujo, reverse harem.
For those who are charmed with English exquisite aristocratic atmosphere, both anime would be the best option.
Very similare to Hakushaku to Yousei.
To start, both animes take place in a European setting. The protagonists have a undeniably die-hard loyal servant that would sacrifice anything to protect their masters, coincidentally, both servants in both animes go by the name Raven. They also possess a very noble and respected status and are expected to fulfill a prophecy, both prophecies involving their ultimate death.
Humans on their own have no directly suoernatural ability (ex. they can't fly or shoot flames from their fists) but with contact from a "different world" humans can get supernatural beings to obey them (In Pandora Hearts there's chains from Abyss, in Hakushaku to Yousei there's various