Magical Explorer, Vol. 6 (light novel)

ANYTHING BUT HEAVENLY! In the depths of a dungeon, Iori finds evidence of the Book of Raziel, a legendary tome that could destroy the world if it falls into the wrong hands.
But when the Three Committees launch an investigation into the book, they discover that the school librarian, Rue Sakura, is actually an archangel! The Academy wastes no time in forming a team of capable students to subdue her, but Rue effortlessly quashes this resistance with her powerful magic. Just as all hope seems lost, however, Kousuke rushes in to confront Rue once again! Does he have what it takes to avert a bad ending of apocalyptic proportions?!