Rokujouma no Shinryakusha!

From DrCoke at MangaHelpers:

Now that he enters his high school career, Satomi Koutaro begins his life living alone in an apartment that only costs him 5000 yen per month, an extremely cheap deal even for this small apartment. There\'s a catch: the apartment is apparently haunted by a cute ghost that has driven its prior occupants away. Next thing he knows, not only is there a ghost trying to drive him out of his new home, but magical girls and other unique female characters turn this small apartment into a battleground of sorts.