Oh yes, Atobe and Sakaki. *sigh* I'm not really sure about it, either. It doesn't seem mentoring, really, but neither does it seem adversarial. It seems more like a mutually respectful relationship.

From the way he stood up for Shishido, Atobe doesn't seem to be afraid of challenging the system Sakaki has created when he sees a good reason to do it. And Sakaki was willing to trust Atobe's judgement. That's the most straightforward way of reading that scene, I think. At the same time, though, something about that scene rubs me the wrong way regarding Atobe's and Sakaki's interaction. So, I don't really know.