Well, Yukari can't promise that there's not future trouble, now. He's going to continue harassing people. But he will keep his word and not lay a finger on Rydia. So, that's exactly what he offers.

"As I promised." A lightly flambouyant bow and mischievous smile.

You certainly appear to be an interesting source to toy with, Kain. You can almost certainly expect him to come tease you in the future.