Azul uses “-san” with all the first-year students, with maybe just one exception: he refers to Jack as “Jack Howl-kun” when they meet. for the first time in Book 3 (changed to “Jack Howl-san” in the manga, this may have been an error).
Azul generally uses “-san” with the second-year students, except for Jade and Floyd, with whom he does not use any honorifics.
Exception: When Riddle is in danger during Book 6 and Azul calls out to him just once without an honorific, but this seems to be a one-time occurrence.
Azul uses “-san” with all the third-year students, with no exceptions.
Twisted Wonderland Reference Note 