Onee Ga Ii Twins (“Sister-Is-Best Twins”) [English], by Satsuki Imonet
Well, here’s an easy scenario. Two younger brothers, twins, express their sexual interest to their sister, she asks for a bit of time to train, and 3 months later, they have a 3some with double penetration ┐( ̄ヮ ̄)┌
Sure, there was even a light comedy note watching the pointlessly earnest sister prepare her body ^^
Graphically, I may be no fan of double vaginal penetrations (my wee-wee touch another man’s wee-wee? [vomit noises]) (plus, it’s a lost opportunity for anal), but I’ll give you that, the sister is spectacularly hot, her preparations and prep show take a fair number of great pages, and the censorship is not that big, so all in all, it’s quality
It’s been released by Fluid_druid, BlueRose and Viacheslavovich, thank you!
By the same artist, I also share Toshi Densetsu Bitch – Joshikai (187 pictures, Uncensored), Hamedori No Yatsu (“That POV Sex Thing”, 92 pictures), @Neighbour, Be Onest and a pack of 4 works (OneHole + That Girl Is A Kunoichi + That Is Also A Form Of Love + The One).
And now, the download & gallery links 
Open the Complete Pictures Gallery
Download the Free Hentai Manga in a Zip file
(19 MB, 20 pictures, English)
Or you can also use the Alternative:
Zip Mirror #1 – or – Zip Mirror #2 – or – Zip Mirror #3
Well, gotta give Mia onee-san credit for making ample preparations to *cough-cough* accommodate both Yuuwa AND Hiroki simultaneously (I don’t always go looking for that sort of thing, but I can’t say I’ve ever seen it before).
And the next time, it will be anal … well, Mia probably made a wise investment in those … er, “training implements” – it’s a preferred alternative to (a-hem) “forced entry” as may be depicted in many stories I generally don’t touch..
Still:

In my head I was thinking of the different montage songs playing in the background while she was working out with the dildos.
Somehow, “Eye of the Tiger” doesn’t seem to work.
I can deal with the shota due to the amount of fun weirdness.