Zero's Familiar: Chevalier Vol. 1,2,3,4 (Manga) (4 Books) Paperback 
by Noboru Yamaguchi  (Author)
  Manufacturer: Seven Seas 
Queen of Hearts

Louise and saito are all still undercover at the Charming Fairy Inn when they get soem bad news―Queen Henrietta is missing!
With their relationship on the rocks, Louise and Saito each decide to help Henrietta in their own way. Louise teams up with a serious, noble-hating Chevalier named Agnès and pieces together clues about the conspirarcy to take Henrietta's throne. Meanwhile, Saito finds a more intimate way to help the queen...