I should have linked to futuransky's panel write-up, since I think you and coffeeandink are saying complementary things.

I would say that in Iemitsu Jr.'s world, an underling can rape an overlord, but an overlord is incapable of raping an underling because Iemtisu Jr. perceives the power dynamic as meaning consent is given by default.

I think that's a really good, pithy way of putting it, and it gets back to the question of power imbalances as setting up all the potential for actual abuses of that power.