Trinity Seven volume 3 features story by Kenji Saito and art by Akinari Nao.

At the Royal Biblia Academy, magical occurrences are commonplace... but ghosts?! While investigating a ghostly happening 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 mysterious babe, and what is she after?!