HivaPrime
Kanan hates the Catholic Church, but his padawan is a part of it. A Christian. Ezra and Kanan's relationship becomes sour after Sabine points out Ezra's religion, and it doesn't get better. Their lessons become nothing but bickering and words of hurt .... until a line has been crossed. Ezra leaves the crew and leaves a note explaining his reasons. Ezra doesn't honestly expect them to come and look for him, and why would they? They've got an atheist for a leader who hates him! There's no way they'll come looking .... right?
Sidenote: description may be changed as the story progresses.