It is also possible to use the same method with consensual sex. In fact, I think it's easier. The lack of it is a conscious choice that I find baffling.
O . o except they do so all the time? It just not all that memorable because it happens frequently, yet not in your face about it.
Just do a speed run thrue earlier chapters. A harem member wiping her mouth here, a different one getting fingered there, and yet another with a pool between her tits.
Hokage is well taken care of offscreen, while leaving the audience mostly blueballed. Can't say if it's intentional or not, but my WAG is that it's ment to drive the audience towards the light/web novel where the MC is plowing his harem of nubile high-school girls every few chapters.