OK, I know this post is really old, but I just want to point out something important: That Keine on the bottom is holding a drill. You know, like in Tengen Toppa Gurren Lagann? That's actually a fantastic pun in Japanese. See, the Japanese phrase that "caved!" comes from involves a (slightly off) translation of the verb horu, meaning to dig. This comes from the phrase ana wo horu, "dig a hole," a phrase which tends to come up a lot in TTGL. Ana wo horu can be misread as ketsu no horu, where ketsu means "buttocks." So "horu" in general can refer to anal sex; in the context of EX-Keine, it is traditionally translated as "caved!" and refers to her shoving her horns up your butt. But it literally means to dig, hence the Simonesque drill-wielding Keine.