On a Friday evening, the seven students in Sensei Naohiro Tomiyama’s Japantown-based Enshin Karate dojo spar with each other in two-minute battles, kicking, punching and pulling at each other’s uniforms. When Tomiyama-sensei’s timer dings, it’s always the same thing: A handshake, a bow and a polite thank you. Then onto the next classmate for another round.

Manners, according to Tomiyama-sensei, are the “most important part” of karate. While it may look — and, with all the shouting, sound — violent, karate, a form of self defense that teaches fast, powerful punching and kicking, has an important basis in respecting others and improving oneself.

Before each practice, Tomiyama says, the group meditates together as a way of getting rid of outside stress and opening their minds.

“When we become pure and empty, all other persons are kind of teachers. If you are thinking, ‘This guy is small, I have nothing to learn from him,’ you’ll never increase your ability,” Tomiyama says. “But if you think you are even, you have the chance to learn something. From that point, naturally we feel respect. White belt, black belt — doesn’t matter. We say‘Arigato gozaimasu.’ Thank you for teaching me.”

Another important aspect of Tomiyama’s dojo is the fact that all students spar with each other. At one point, a white belt looks up more than a foot at an older student wearing a black belt. As Tomiyama starts the timer, the younger fighter does his very best to hold his own in the round.

In traditional dojos, Tomiyama says, students typically face people of similar size and strength. But Tomiyama disagrees with that training method.

“If you practice with the same size person, that technique just works for that person. In the world, there will be big guys, small guys, skinny guys, muscle guys. So I want to give them the chance to see all different types of person,” Tomiyama says. “It makes more creative thinking.”

As a young child in Japan, Tomiyama first studied kendo, partly because there was a school near his house. But after seeing Bruce Lee movies at age eight, he became fascinated with karate, which, at that time, had not yet become popular. When a karate school finally opened near him when he was 13, he immediately signed up.

After studying karate for 10 years, Tomiyama appealed to Joko Ninomiya, the Grandmaster of Enshin Karate, who was teaching in Denver, Colo., to take him on as a student. Tomiyama became an uchideshi, living at his teacher’s home and studying full-time.

“My situation became heaven for me, because I can just focus on karate,” Tomiyama says. “Also, I love American culture and wanted to study English and open my eyes.”

His studies paid off. In 1992, Tomiyama became the Enshin Karate World Champion. For the next few years, he taught karate in Tokyo. Then he decided he wanted a change, remembering his positive experience living in the United States.

“I wanted to start from zero,” he says.

Tomiyama spent three months traveling around the country, scouting different cities as possible locations to open a dojo. As a way to interact with strangers, Tomiyama staged impromptu public performances at shopping centers, breaking baseball bats to show his strength, then talking with audiences to gauge potential interest in studying karate. But after two days in San Francisco, his search for a place to settle was over. Japantown, the ocean, kind people and good food made a “big impact,” he says. “San Francisco was very special for me.”

Tomiyama, who opened his Japantown dojo in 2001, says that he loves teaching and learns a lot from his students.

“I have more than 40 years of experience with martial arts, but every day is fresh for me,” Tomiyama says. “Every day’s class is different.”

In the Friday night advanced class, an exciting moment comes when one student succeeds in throwing another to the ground with a huge thud.

Tomiyama’s face lights up. “Great!” he says. He paces for a minute as the students continue to spar. Then he turns back to the student. “Do it again!” he urges with a sly smile.

With all the kicking and punching — and in some cases, getting thrown on the ground — it’s hard not to worry that the students are in some serious pain.

“Yes, it’s painful,” Tomiyama acknowledges. “That’s one of the most important parts.”

Think about video games, Tomiyama says. “Kids play games and kill people in the game. Of course, (they don’t) feel any pain, just giving pain. When you give pain to other people, you don’t feel other people’s pain. When I feel pain, I can understand other people’s pain… I feel more alive.”

Tomiyama is quick to explain the goal of karate is not aggression, but self defense and self improvement.

“It’s not for fighting. It’s to find weakness from the training,” Tomiyama says. “Most people want to ignore their weakness, but we have to face it seriously. And when we face weakness we can change something. That’s karate training.”