Who knew?

1) Demons of Gehnna 2) Exorcists 3) Vampire Hunters 4) Vampires alike. What could get worse? Mephisto and Kaien Cross are good friends, resulting into Rin's gang being dragged into Cross Academy as Day Class students. But, things aren't the way they seem, and many things could happen if you have all the 4 of the above.(PAIRINGS?: Find out!)