Raikou Mama To Nurunuru Shitai [English], an hentai doujinshi parodying the Fate Grand Order game, by Navier Haruka 2T
That cover. Jeeeeeeeeeeeeeeeeeeeeeeebus
In this share, Raikou (googling led me to the name Minamoto no Yorimitsu, though?!? O_o) decides to please her master Gudao with lotion play, she puts on a swimsuit, and lots of rubbing and French kissing later, it’s time for anal sex. The art is fairly decent, the censorship is hardly a thing, it’s a fine usable read
There’s one thing I didn’t understand, is that part of their erotic play, she and the MC playing as mother and son? Or is it supposed to be actual incest? If someone could clarify, please… I’d be grateful…
Thanks to Cgrascal for this release!
By the same artist, to this day, I also share Nuru Never Yuri-izm, Nuru Never Drain 3 and Oneshota JK Soap.
And now, the download & gallery links 
Open the Complete Pictures Gallery
Download the Free Hentai Manga in a Zip file
(21 MB, 17 pictures, English)
Or you can also use the Alternative:
Zip Mirror #1 – or – Zip Mirror #2
From what I have read she treat her master in a maternal way, so it a sort of play. Her design was made by Raita and in some way it´s similar at how Misa from his “Mahou Shoujo” books treat the main character.
Raiko is insane, she might look and act like a normal girl but she has mental issues. She thinks of her Master as both her son and lover and is ready to kill any other girl who comes near him.
Yes, you are absolutely right about this very important subject, it is a real pain to find good nuru-massage here in west.