 If you liked
Fate/stay night
|
 ...then you might like
Yumekui Merry
|
Both series feature "master-servant" relationships where an ordinary human being is paired with a character who possess superhuman abilities. The pair is bounded, and the death of either side will greatly affect the other.
Battles occur behind the scenes, yet the the consequences are seen in the real world.
There are mystery elements in both cases, and character backgrounds are slowly unraveled through battles.