I used to build and fly kites like that, but only one in the air at a time. Flying THREE at once, that guy is amazing!
Called fighting kites, when used in competition the lines are coated with crushed glass or abrasive. The object in a fight is to sever your opponents line then wrap your line around the cut line, capturing your opponents kite.
Flying one kite is challenging because the kites trade stability for maneuverability. Flying three is frickin awesome!
I have a daughter. I tell her, "911 is what you dial after you're raped. 1911 is what you should have before they try."