Been searching for this one for quite a while, and thats the only trace i stumbled upon recently. The hentai is full coloured and is about a brother (i think) scholding his sister and ends up cumming inside her.
>>14930153
[Rokkaku Yasosuke] Shirikatsu ! (COMIC Shitsurakuten 2014-11)
no lie, this took me 30 seconds. went to nhentai and searched full color, sister, tanlines and it was on page 5 or 6.