Nee-chan Ga Ore O Suki Sugiru (“A Story Of My Onee San Who Loves Me Too Much”) [English], by Haguruma
Consent was asked, and given, several times, so we’ve miraculously escaped the typical domination + yandere scenario I thought was coming. Allow me a sigh of relief
In this share, a stepbrother finally discovers his stepsister is crushing hard on him. As he doesn’t dislike her and it’s her birthday, he gifts her what she craved for.
The girl made kinda crazy faces several times (that’s why, with the few random pics I had opened to see if it was worth a download myself, I got the wrong impression), the boy appears to be an M, but I don’t have particular reservations about the rest, I think it should be a worthy read for most of you guys
Just see for yourselves, and if it’s right up your alley, have a good time
Thanks to Pingu and Xinsu, from Xinsu Translations!
By the same artist, I also share 5nenme No Houkago and Niwasaki Poolside.
And now, the download & gallery links 
Open the Complete Pictures Gallery
Download the Free Hentai Manga in a Zip file
(35 MB, 34 pictures, English)
Or you can also use the Alternative:
Zip Mirror #1 – or – Zip Mirror #2 – or – Zip Mirror #3
¯\_(ツ)_/¯
Another time, place and artist, we’d definitely be saying (as Oliver put it once): “YAN-YAN!” And as for the “biology failure” (cells being replaced by semen ….. WAIT, WHAT?), whatever the artist wanted to convey escaped me.
But it turned out to be mutually accepted by both step-siblings, so I say to that:

Sooooo….if her cells are now made up of Haru-kun’s semen, does that mean she’s now a sperm Homonculus?
Looking at that face, mouth, and body on the girl, this was borderline monster girl hentai.
I think even succubi would be saying, “Damn, girl, you need to take it down a few notches.”
Oh, who am I fooling? That was righteously intense! Like sanity is all it’s cracked up to be!