There isn't any, really. Personally I think fanservice ruins a show, especially one with a well written story, and Tutu had very little if any at all.
I didn't really consider Ahiru running around naked to be fanservice but I guess that counts a bit, though it's not really detracting. There was also a scene where she was being strangled by Kraehe's tentacles, which was fanservice-ish.
But otherwise, yeah, you're in trouble!