An old hentai that have the son and mother incest because of the father dying will and after sex, the son reads the will and the will contains the father teasing the son

I remember one like that.......something like the dad had left he wanted the son to get with mom in the will but she kinda hid the fact that it was actually his father's wish from him until afterwards and the son was feeling all guilty about, you know, boinking his mom and all 😀 .......sorry, I remember it but didn't save it anywhere, it'd be like finding a needle in a haystack now >_<