We must remember that its all visual anyway. And in this case it would stem from a desire to have a situation or have a character thats not cannot be had but is no less real for it.
Example:
You can't place Buffy the Vampire Slayer (nor Sarah Michelle Gellar either) in this world as you would want them. Buffy Summers is a fanciful character. Gellar is an actress playing the part of this fanciful character. Suppose there was a tickling scene (maybe there is, I don't know I'm not a fan), and suppose Buffy is ticklish. Yes, thats real, but Gellar being ticklish may or may not be and the two are two completely different people.
So if you're getting your satisfaction out of this proposed scene because of the actress, then its because of that, not the character or the event, or what is happening, because THAT stuff is real in the contexts in which its happening.
See, the trick of movies, tv, anime, whatever medium is that we must try and keep our minds in perspective and into the world and reality the story takes place in.
When people say things objectively, things like "yeah right, that could never happen, thats so fake!" they have forgotten that its real and possible there, to those people, in that world. And provided that world follows and is binded somehow by the real reality of this world then one form of tickling as in anime, over another unreal character (ie: Buffy) doesn't make for a whole lot of difference if you get the same visual satisfaction out of it all the same.
An anime character getting their foot tickled for example is no more unsatifying than another fictional character getting the same treatment and they're portrayed by an actor. People make a difference because one is completely tangible and the other is not. But if the feelings, emotions, and nature of the situation was still provoked and felt by the audiance than its just as real. Thats what movies, tv, and yes, even anime aim to do even. They exist non-existantly.
Its not a matter of whether its contrived or not, or fake because in this medium (that io tickling) both are fake in actuality, but very real in presentability.
I'm a voice actor, maybe I'll be a regular actor someday too, but I don't see any difference between my bringing life to a character through my voice or by me physically acting out this role. Why? Because my heart and soul is INTO what I AM doing whether its verbal or physical, or both. Either way, the character is fictional, even if I more physically embody said character. The character is no less believable because I was not there to physically give it substance. Its made whole and alive by my talents as an actor. I give life to something which would otherwise be mute. In turn, animators give movement to something which would otherwise be idle.
Its the same for this topic in terms of what is real and what isn't real. None of its real. Its all fiction. But its real where it exists. To be technical, if an animator can draw a character to look exactly like real humans (and they can and do) and what they are doing with the characters are as realistic by lively standards, then I don't see how there can be a difference between this and watching something real. They're both real because they've both provoked the same kind of feelings.
If they haven't, then its because people have created a subconscious doublestandard, where our dear Buffy the Vampire Slayer is more real than Line Inverse and Witch Hunter Robin (for example).
Its all the same, just a different medium through which you're viewing this fantasy. Unless you created the video or had it created for you exactly as you wanted it, its not real. Even then its fake, as you are setting up a situation thats wouldn't have happened otherwise. Just because they're human beings and theres flesh and bone and life that makes it real? Not really. You can never see exactly what you want to, even if you are creating it.
I'm an artist, and even I can't do that. I can only strive to achieve the image I have in my mind and hope and try my best that it comes out as close to what I had imagined. The same is true for those in the movie industry and even the humble tickling video producers. The same is true for anyone that creates anything, past, present, and future.
They can only give you a glimpse of what could be real and would be otherwise, but something that not actually is.
Anime is real if it delivers an emotion or feeling.
Fictional characters potrayed by actors are real if they deliver an emotion or feeling.
Written characters made tangible only by the words that discribe them ARE real if they deliver an emotion or feeling.
See, its not the characters that are unreal, its the situations they are in. And as I've explained, those can be real, but the medium through which they are presented to you are not a factor as they will never be anything more than a visual image to you.
I know this just seems like common sense, but I don't think its used enough, and its always interesting the perspective that can be reached through it.