Furrin_Gok said:

Dude... She's a snake. Her "Underbelly" is the part of her body that would be downwards at most times. If the anus was on the top side, she'd be pooping upwards, which would leave a mess all over her. Not at all healthy anatomy. Having it on the same side as the vagina, though, leaves it falling out and away from the body.

Ok, I get it now.

See, this was the first time I had seen these enemies and I thought I was looking at legs so I figured they were anthropomorphic like the Man-Serpents from Dark Souls, but they're more like a naga.

That anus is still pretty convex, though.