I think, Moe does enjoy herself, when she is dominating others, you can see her smiling a bit on some pages, and she is properly blushing while having sex too. But she isn't an S, so you won't see her smile or enjoying herself, when hitting others.
Yes, most of the time she has a blank expression, but her face has been that way, since Ran refused her, it doesn't mean she is faking it, or not enjoying herself, only that she's still heartbroken.
Well, that's how I interpreted it anyway.
last edited at Jun 21, 2015 5:31AM