Danh Phi Ngoc
Thanks for all of your comments.
but no one has answered what is the purpose, reality behind this clip?What did Sensei try to demo?
Haha. I think the opinions expressed about the reality behind this, is that the guy doesn't have magic powers, and what he's doing is an embarrassment to the name aikido; but a few people/one person(?) argued that he was using the power of his mind to make a load of people who had the 'mindset' of earnestly attacking him fall over.
So he tried to demo his mental powers, is the best/only explanation given, I think.
Don't worry about it, dude: there are a few people doing this kind of thing - just focus on doing aikido: it's irrelevant right now - you get ki balls at 12th dan, by which time it'll all make sense.