Holy moly!!! Great job! I would have loved to see the other girls from the first chapters again, at least a threesome with the sister and my favorite, the blonde, who had a beach chapter as an introduction. But oh well, I remember that on his Twitter account, around 2010 or earlier, the author had uploaded a picture of the two sisters and the blonde naked, lying on the bed and opening their legs to invite the protagonist to action. It's a shame that the author deleted that image, among others, from his account now.
@jakalsito Considering the series started in 2014, either it was a really early concept art or you revealed your time traveling powers. :) (I think I remember that picture, but it was posted way later IIRC.)
@Faeldrin I didn't say it was the exact year XD, but thinking back, I remember the image was available after the chapter where the older sister and the protagonist begin their battle of wills was published. I hope the author republishes those images, even if it's just as a bonus in some tankōbon he releases, if he's up for it. I still regret not saving those images T.T