[Mochichimaru] Kyonyuu Osananajimi, Kuchidome wa Oppai de

Looks wholesome but judging from the comments, the author does ntr too. Shame.

The girl's name here is Aoi and the guy is Hiroki, her childhood friend. In the "NTR"/BSS doujin the others are talking about the girl's name is Mizuki, the little brother is Keigo and the older brother is Daichi. These are two completely different stories, not a prequel-sequel. The girls are just suffering from sameface syndrome due to this author's way of drawing girls.

My god this was the original of that monstrosity of a family?

this is better than second version

I see, so this is the prequel

To comment below me. How can you predict the future???

I guess you gotta do NTR to sell your works