Reverse Clapping

A person(?) caught on TV doing reverse clapping

(Translated from Japanese by Saya)
There was once a couple on a date who decided on a whim to visit a haunted place, just to have some fun.

But once they got there, they had a fall out, and the boyfriend angrily drove away, leaving the girlfriend behind in the haunted place.

A few minutes later, however, he calmed down and, realising it wasn't a good idea to have left her all alone in a haunted place in the middle of night, made a u-turn to go back to the haunted place.

She was still there, and they soon made up and decided to drove back home together.

On the way back, they saw a boy waving his hand at them. But instead of showing his palm, he was showing the back of his hand while he waved. 

"Poor boy, what is he doing at this time of night? We should give him a lift," the girlfriend said.
"No way. Don't you know that if someone is doing an action that is in reverse to how it is normally done, then that someone is not of this world?" replied the boyfriend.

"Wow, really? How come you know so much?" The girlfriend clapped her hands.
She was hitting the back of her hands together.