Despite the obvious nipple torture, this photograph is really all about faces for me. His look of pain and her sideways glance. You can read a lot of different things into that sideways glance.
Is she looking away to fully enjoy and focus on the screams of pain she’s generating? Is she so expert that she doesn’t need to look in order to grind his nipple with her heel? Or does she not care where she ends up stabbing him? It’s going to hurt wherever it goes after all.
Found on the 333 images tumblr blog, but originally from ruero.com.