More C.C. Butt Magnetism
The more I see of this girl, the more I'm convinced that she has magnets in her ass that always draw it toward the audience viewpoint. Like regardless of what position her torso is in, her ass will just shift towards us.
Alternatively, like I speculated last time, maybe her butt is just tidally locked with us.
(Official art from Code Geass: Lelouch of the Rebellion, Sunrise, submitted by anonymous)