Fapping to best female friend fucking?

Okay so here is another hypothetical question for you. Think of your best female friend (that you have not sexual experience or history with). The question is would you fap to her fucking? is this an obvious yes or are there some lines that we should just leave be and never cross?

And you can broaden this question to would you ever fap while watching people fuck. Obviously for the sake of this question you can not join in. Leave your comments below!