The Eminence in Shadow Light Novel 5

All is well at the Midgar Academy for Dark Knights, but then something wicked suddenly draws near: The students are vanishing one by one—even Cid’s older sister Claire! Zeta of the Seven Shadows sets off to investigate while Cid and Alexia embark for Claire’s room where they find…ancient scripts, a cool magic circle, and spells that seem like they have great meaning and yet absolutely no meaning whatsoever?!