Sakamoto Shoma has been a sumo wrestler, or rikishi, for 10 years since the age of three. He gets up at 6:00 a.m. every day and tidies his dormitory room before breakfast at the training stable, or heya, where young novices live according to a strict routine.

At the heya, a group of brawny and disciplined teenagers would sit around the table, wolfing down a plethora of meat dishes and destroying one rice bowl after another.

Eating is part of the training. A sumo wrestler's daily caloric intake is double that of the average man. Sakamoto loves grilled meat and can eat 60 pieces of sushi in one sitting. But even when they are full, the boys continue to fill their stomachs with more food in order to get even bigger.

Acquiring an imposing physique is not enough. The demanding training that follows requires tremendous perseverance and passion for the sport.

Sakamoto heads straight to the ring for practice every day after school. Despite his heavy appearance, the teen is surprisingly agile as he warms up with push-ups and stretches.

"The thing I like about training is when I win during a tournament, I realize that all of my efforts were not a waste of time," he said.

Sturdy and focused, Sakamoto is ready to overwhelm his opponent, pushing, shoving and throwing him off balance to claim victory.

In sumo, a wrestler wins by forcing his opponent out of the circular ring, or dohyo, or into touching the ground with any body part other than his feet.

The ultimate goal for young men like Sakamoto who dedicate their lives to sumo is to become a yokozuna, the highest rank for sumo wrestlers. The only way to move up the ranks is through fighting in official tournaments.

Sakamoto said his favorite thing is to defeat someone who is above him.

In Japan, a yokozuna symbolizes strength and dignity, and thus commands a great deal of respect. But to become one is extremely difficult. According to the Japan Sumo Association, a total of 72 sumo wrestlers have earned the title in the sport's history.

Sumo is a quintessential part of Japanese culture dating back centuries. With a heavy emphasis on rituals, sumo is a way of life dictated by ancient traditions. The rules which rikishi live by, from the way they dress to how they carry themselves during bouts and in daily lives, evoke the way of the samurai.

The rikishi adhere to a strict ranking system. Yokozuna is the pinnacle of this hierarchy and is almost a kind of a religious figure in his own right – an embodiment of the samurai spirit.

The referee in sumo is called gyoji, who dresses like a Shinto priest and performs a purifying ritual ahead of a match on the dohyo, which is also considered sacred.

"It is a cultural sport that represents Japan," Sakamoto said. "With such a great culture and history, I think sumo is a great sport."

Recent years have also seen a budding amateur scene of sumo for women, who are still barred from the professional arena.