Actually, it's known as a utsuri-goshi/switching-hip. By controlling the guy's head and leading his body one way, he quickly switches the direction his head is going while his legs are still going the other way. Once his legs go up in the air, all he does is lead they guy downward by his hands. Unless the other dude knows how to fall, hell fall on the back/side of his head (which he does). Notice that he starts to get up and throws down his gloves and headgear only to stumble back onto his ass?
That is probably one of the most beautiful and brutal Kosen Judo throws (I don't think it is part of the Kodokan curriculum of techniques).