Codebreaker or Nutcracker?

I need help on breaking this code:

jymrmpibftxkmnmstqvxz

Here is the hint:

"One left, two right, four forth and six back. And again. What does it form if left is back and Ceasar is not only an emperor?"

I think it has something to do with ancient cryptography, because Ceasar was the first to use coded messages in wartime.