This is a true happening not so long ago.
My mid 30's daughter who is living with us is no stranger to my naked body. I once walked into the kitchen from the bedroom naked thinking she wasn't about and just stood there doing something, though I forget now what it was.
A few moments later she came into the kitchen and saw me full frontal. Her first reaction was to look down at my then limp penis for a moment or two then just carried on what she came into the kitchen for. This sooo turned me on, even though she is my daughter and I'd have no inclination to mess with her.
I must say that I don't have a large penis. It only comes to about five inches when fully erect, but it's good enough for me! I do however have quite a bush of pubic hair around it, so it looks smaller than it really is.
After that incident I had no worries about her seeing me naked which she didn't often but that incident so turned me on that I quite literally planned a few times to walk into a room naked I knew she was in. This always turned me on to have someone other than my wife seeing me naked. But that's as far as it went at the time. However a short while ago things took a different direction.
A few weeks ago when I was left alone in our house, my wife being at work, and my daughter having gone out for a walk as she often did, I took the opportunity of stripping naked and because my laptop was in the kitchen, rubbing my cock with baby oil whilst watching a very short series of porn videos. These so turned me on and I was rubbing away with my baby oil all around the tip when in she walked. She saw me full frontal, totally naked and rubbing like mad on my very erect penis. There is no way I could stop at this point so just made the most of it.
I told her what I was watching and she came to take a look.
'This is so good', I told her. 'It isn't every day a daughter gets to see her dad masturbating'.
She watched as I started to pant because I could feel the cum rising up inside my penis. I think it was urged on partly by her being there watching me. Finally I came in my hand and held it out for her to see.
She didn't say anything but looked at my penis throbbing, my cum in my hand, then she went to the refrigerator and began getting things out of it as if nothing had happened out of the ordinary.
This was bit off-putting and made me feel rather guilty but I guess she must have been a bit embarrassed and so decided to ignore it.
There have been other occasions since then when I've walked naked from the bedroom into the kitchen when she's been in her own room, and she's come through and seen me naked, but she takes no notice and just gets on with what she came in for.
Perhaps just as well.