Aragne: Sign of Vermillion

Life could be better for shy, anxious university student Rin. The apartment she has rented is hardly the sunny palace the rental listings suggested. The housing complex is rundown, grim and haunted by troubled souls lurking in dark corners. Ghastly crimes are occurring in the vicinity. And a grinning stranger makes his unsettling presence known. Beyond all this, Rin is coming to realize that something even more sinister is manifesting itself, something at the cursed crossroads of mythology, monstrosity and medical science. Determined to find out more, Rin visits the library, where she meets a sympathetic young staffer. But what she learns does not begin to put her mind at ease.

Synopsis from Anime News Network