
There’s gotta be a way to put it all in safely, right...? Otherwise how does fisting work

For the sake of spreading human anatomy basics (and preventing misconceptions all over) - there a things that WILL work. Then there's things, that MIGHT work. And lastly, there are some particular things, that only work if its an endoscope, you see.
http://www.mangago.zone/home/photo/3410324/
(As a former nurse, whenever I see some anatomically questionable practices promoted I can't help but hear Peter Quill:
"Let's talk about this plan of yours. I think it's good except it sucks.")

The rape-turns-to-Love trope is so overused and kazusa was awful to yukinari, but surprisingly I was touched by the ending

Yup. I really hate rape cliches but while this was a typical, I rape you and it's your fault, kind of cliche (the tragic past isn't going to change my mind on this any, either), Kazusa actually learned how to not be a douchebag, anymore. That IS rare. So I really don't understand commenters who think this is worse than the other (majority) rape cliched versions of storytelling I've seen out there. And no personal growth displayed in the rapist character, either.
Bow down to your new goddess Kalifa