When you really think about it, torenas are not capable of consenting properly to umapyoi. These are ningen with a predisposition to see umas going fast and going "u-uuUUOOOHHHH I'M GONNA SCOOOOOUT" and barely capable of any thoughts outside of training umas. So when these same umas whose running fried their torena's brain go on to engage in any kind of carnal relations with their torena it's essentially unethically taking advantage of the mentally challenged, not to mention that when torenas get confused and scared about umapyoi being forced upon them they have no recourse since they physically don't stand a chance against their umas