It’s called Bo-Taoshi (Wikipedia link) and basically is a Japanese combo of Capture the Flag, Red Rover, American football, and kick-boxing.
No wonder Japan doesn’t play American football… they have this. If watch closely you’ll see plenty of face-kicking, shirt-ripping, and general macho-ness.
This looks amazingly fun. If there was an event like this in the US I think I would try out.
If you’re still looking for more Bo-Taoshi, try this clip on for size.