This is just straight up hentai. It feels like the author want to write hentai, but he also wants to get serialized. So, he took middle path and created this half-assed hentai. He should just write full hentai, but that wouldn't be profitable.
You know one hand it's nice to know the author has the support of people willing to entertain this. On the other hand it's not nice to know that nobody seemingly reined in the author's...highly suspect idea. I can barely imagine how the meeting for this went.
Nevertheless thanks for the translation. Despite what I said I kinda like this. It seems very horny and fun and I dig those in the stuff I read.
Mangaka: "So the brother has a wet dream and the blood-related sister comes in and licks the cum off of him and she later lets him use her mouth as a semen receptacle... I... I'm sorry, it's too much, isn't it?"
Editor: "Actually, this isn't even the most degenerate thing I've had go over just today."
Some of the shit manga editors have to see... I wouldn't be able to do that job.