I liked the story quite a bit. It has a nice theme, and I generally like stories that go into what the characters think or feel, like the guy watching the girl get tickled and noticing his responses to seeing it.
Nice story! Welcome to the world of TMF writers. I'm looking forward to the second part. I liked the set-up and the whole plot. It's interesting to see someone forced to watch someone being tickled, I thought that was neat.