@Necha
She specifically stated that the ropes could probably be tightened more. I don't know how long she was tied up but if it wasn't tight and it wasn't too long there's little chance the rope will leave marks that were visible. Maybe if she moved around a lot but that didn't happen either.
@Chrona@Necha Even when leaving enough space to be safe, the ropes should still leave marks, albeit shallow ones. But they fade rather quickly, so it's not a big deal. And someone with Ayame's skill would really only take about roughly 7 or so minutes to finish a maeteshibari. Then some play after that, would only be about 20-30mins. So they would probably fade by the time Aoi is ready to go home.
@youkari
I guess I should have been more specific and stated that it wouldn't leave any lasting marks, since the concern was other's would see it, but yes that's what I was basically stating.