Trinity Seven, Vol. 3: The Seven Magicians - manga

At the Royal Biblia Academy, magical occurrences are commonplace...but ghosts?! While investigating a supernatural rumor at the school, Arata and his friends find themselves trapped in the Eternal Library--where a pigtailed beauty suddenly appears before their eyes! Just who is this very familiar-looking babe, and what is she after?!! It's Volume 3 of this romantic comedy and sometimes-serious wizard school story!