There's one ntr manga where the first scene in is the main character jacking off while sniffing his's mom's panties. i think literally in the first panel he's thinking "Mom's panties... the smell of mom" and then she walks in the moment he busts and says "hmm did you call for me??"
i think she ends up fucking his friend in the next room over while the son listens. Can anyone help me out? I think it's one of the more popular ones. The mom has red hair if that helps