Hundreds of bodies slam violently against each other, hands pull at limbs, feet kick at heads. It's a chaotic, violent assault -- and it's taking place at a school sports day.
While it may seem like mayhem, this is Botaoshi, a traditional organized sport played all across schools in Japan.
The basis of the game is comparable to a round of Capture the Flag: two teams challenge each other in an effort to reach a pole protected by an opponent.
But that's where the similarities end. Each game can feature hundreds of players, the safety precautions are minimal, tensions are high, the games are violent and undoubtedly dangerous.
"It's rugby, it's NFL, it's wrestling, it's sumo, it's crazy it's what it is. I've never seen anything like this," says CNN's Coy Wire while watching a game in Tokyo.
Human shields and a ninja: How it's played
Simply put, the aim of the game is to topple over your opponent's pole in around two minutes.
To start, a small group of defenders referred to as the Pole Support group lock their legs at the base of the pole, forming what is the base of a human shield.
Then, a second and larger group forms a thick layer of bodies in support of those at the base.
A third and fourth cluster, referred to as the Interference and the Scrum Disablers, form a layer of aggressive defense -- they are both tasked with actively pushing back any attackers from their human barricade.
The role of a Scrum Disabler is slightly more specific -- they are tasked with protection against Scrum attackers, or members of the opposite team who have launched themselves atop of other players in an effort to springboard through the barrier.
Finally, at the top of the pole sits a lone defender -- referred to as the Ninja -- as a final layer of protection. This player kicks back at attackers and uses body weight to balance any attempts to push the pole over.
The poles can reach anywhere between 10 to 16 feet, and although official pole-toppling rules can vary, it is commonly agreed that a 30 degree lift off the ground is considered a successful assault.
Origins of Botaoshi:
The origins of Botaoshi remain a mystery. However, one of the more common assumptions is that the sport began in the 1940s as a form of military training.
Although that theory is still unconfirmed, the game does feature prominently at the nation's military academy today and is played annually by cadets at Japan's National Defence Academy, surrounded by hundreds of spectators.
More common, however, is its presence in schools across the country -- from elementary to high school levels.
The tradition (and in some cases, gaming tactics) are passed down from school year to school year. Taking home the winning title is something the students take very seriously.
"It's so important. Botaoshi has been played in my school annually for 50-60 years and every senior student is dedicated to this game," says Iko San, a botaoshi player at Johoku Junior and Senior High School.
"It's so important for us at school sporting events because it is part of our identity."
Amidst the mayhem, students find beauty in the tradition.
"It was chaos, people are running around everywhere and we don't know what's going on. Although we were completely mobbed in the crowd, we continued to try and pull the pole down. I think that's the beauty of Botaoshi," says Ikko Chikusa, another botaoshi player at the school.
With over 100 bodies slamming against each other and young players still in their teens, questions about safety inevitably arise.
There are some rules in place. Shoes, for example, are banned -- but only because kicking (including kicks to the head, if necessary) are common in the game.
Players have almost no protection aside from a soft padded helmet, and occasionally some knee pads. But, for some, concerns over potential injuries caused by the game are overshadowed by a sense of pride.
"As a teacher, I do get scared because I don't want anyone to get hurt. But, as a man, it makes me feel comfortable and proud of them. I have been here about eight years and I have never seen student get hurt," says Yukisan, a staff member at the high school.