In Japan, if you really screw up, just saying you're sorry won't cut it. You might have to grovel. And this is some of the most extreme Japanese grovelling you'll see.
As previously mentioned, prostrating yourself (土下座 or dogeza) is a way to apologize when words alone won't cut it. It's a pose that empowers the person you are saying sorry to and leaves you vulnerable—your neck is exposed, which when Japanese people carried swords, put you at another's mercy. It has also been used when people met or encountered nobles.