I agree, and while most understand that rape is not okay and people don't just get over it like it was nothing. Younger people do read these, despite it being adult content. I've seen on another manga featuring rape a person say "it's not rape because he liked it" and that is my biggest problem with normalizing rape in this context. It's hard to feature rape in a manga and have EVERYONE understand that this type of fictional rape doesn't represent reality, yes most will understand but the few is concerning. I pretty much have the same reaction to rape in manga at this point. It does nothing to/for me. But beside the fact the controversy on rape itself, hasn't the whole rape to move the story along gotten stale? In most manga it's boring and predictable at this point, so you would think we would have dropped this by now.
Change takes time, but at least its happening. Also, you did bring up something I wanted to address, but decided not to: 'Younger people do read these'. Now I am not pointing fingers at 'young' people, I am only drawing from my own experiences with yaoi. When I first started reading yaoi, I was 15-16. I was quite sheltered, and didn't really understand rape. The thing with these mangas featuring rape, they don't outright declare it as rape. It's implicitly understood by the reader, that 'no means no' and this is rape. I didn't know that, so when I would see the victims say 'no, dont...' etc. I couldn't take it seriously (also the author's portrayal didn't help either). I thought they were declining to have sex because they were of the same sex and not that it was a physical violation of their body. And my thoughts were almost always: don't worry the seme (I don't want to generalize that the seme only do the raping, but back then that was the case) will take care of you, and see you like it, now was that so bad. So yea, I had such moments and only slowly did I realize how fucked up I was. So to those justifying rape in manga, 'yo, its fiction, so chill', you've already been influenced by yaoi's portrayal of rape. You are justifying something that is morally wrong. Regardless, just remember, there is a very thin line between fiction and reality.
So, this one-shot features rape. Nothing new. Yaoi feeds on rape. I dont know why, but authors seem to think love can't blossom w/o rape. Well, that's fine too. It's their opinion. Nothing wrong with having opinions. The problem with my statement: I have just normalized rape in yaoi. Moving on, authors also seem to think rape is not a big deal, since all these victims recover almost instantly. Hence, rape becomes a means to an end, w/o it our MCs wont have their happily ever after.
Now, I get the whole 'It contains rape, don't like, don't read'. I am not a fan of rape, no one should be: it's a violation of the worst kind. But, I don't shy away from it. If a manga features it and handles it delicately, I especially love that work. It not, I am rather indifferent, I just ignore it so I can get to the better aspects of the manga/ manhwa.
But it just occurred to me, if rape was normalized on the big screens? How horrifying is that notion. So if it isn't fine on there, it shouldn't be fine on here. Especially when its handled so dismissively. Art imitates life, and life imitates art. There are consequences to such portrayals and we shouldn't let it slide.
However, I have noticed that many authors are moving away from this trend and have produced wonderful heart-wrenching mangas/ manhwas. So, i still have hope.
Also, there really isnt anything one can do if an author decides to feature rape, its their creative freedom. It's a waste of breath to condemn them. However, its within our abilities to encourage authors who don't feature it or at least not dismissively. If there is enough support for these authors, others are likely to follow. After all, its simple supply and demand.
My final thoughts on this manga: It really hurt to read this.