Futari No Shikaeshi (“The Double Revenge”) [English], by Oden70
How should we call this, counter-cheating? You catch your girlfriend with another man, so your own revenge is to have sex with her older sister, finally accepting the moves she’s making on you? Something like that, I guess ┐( ̄ヮ ̄)┌
To quote the male MC: “I’m not able to think straight. And to be honest, I really don’t care anymore.”
There’s more plot twisting in the end, but that’s the gist, basically ^^
On the one hand there’s huge white censorship and odd helium-filled boobs (by the looks of them), on the other hand it’s nice powerful action, so, eh, chances are this share will please a good number of people, enjoy!
Thanks to whoever is behind this release!
And now, the download & gallery links 
Open the Complete Pictures Gallery
Download the Free Hentai Manga in a Zip file
(19 MB, 18 pictures, English)
The occasional rant about excessive file sizes: I downloaded it myself as a 57 MB archive. Pointless. You won’t notice any difference with the naked eye, absolutely none, but now after a meek recompression, it’s only 19 MB, enjoy
Or you can also use the Alternative:
Zip Mirror #1 – or – Zip Mirror #2 – or – Zip Mirror #3
The weird thing is that this is not fantasy, this actually happens. Where a sister steals another sister’s man, and a double swap is executed. Can’t cite examples, but have heard interesting stories from couples.
Man, I really hope that was the author’s first work, because wow, that really felt like an author’s first work. Which means the next one has a lot of potential, though this one had its strengths as well.