TOKYO — When my 6-year-old son recently joined a local kendo club, I found myself at Yamato Budogu, a family shop that first specialized in equipment for the ancient Japanese martial art in the 1930s.

Kendo — the Japanese characters mean “the way of the sword” — is a form of fencing that uses bamboo swords and protective armor. And equipment for what is considered modern kendo originated in the 1700s.

My son needed a beginner’s outfit: a shinai, or bamboo sword; a dogi, the kimono-like top; and hakama, wide-leg trousers. A uniform for an older or more advanced practitioner has four additional items: a men, a type of face mask with metal bars to protect the head and shoulders; a do, or breastplate; kote, gloves to cover hands and forearms; and a tare, a thick cloth belt with flaps to protect the hip area.

“I can make every part of the uniform and repair everything,” said Kiichiro Ito, 83, the president of Yamato Budogu Seisakusho and a bogu craftsman (bogu is an inclusive term for kendo equipment).

His specialty is the men, the face mask. Its fabrication begins with two preparatory steps: layering pieces of cotton, wool and other fabrics to form a protective pad and wrapping rice straw around the rim of a manufactured metal face grill, called the mengane. The straw provides a base so the pad can be hand stitched to the grill, and the edges of the whole assembly is then bound with strips of rawhide to reinforce the structure and improve the piece’s overall appearance, Mr. Ito said.

The process takes about two weeks of work to produce the basic model, while higher-end models, which require finer stitches and decoration, can take as long as three to six months.

Mr. Ito also collaborates with other bogu craftsmen around Japan: For example, one of them, in Saitama Prefecture, north of Tokyo, specializes in aizome, or indigo dye. The artisan dyes textiles thread by thread and then sends rolls of fabric to Mr. Ito’s atelier, where it is cut and added to protective pads. (Other indigo-dyed textiles from artisans in other prefectures are used for the cotton dogi and hakama set.)

The family business was started by Mr. Ito’s grandfather in 1936 in Aoyama-itchome, an area in southwestern Tokyo. Over the decades the workshop moved, shifted to equestrian equipment when some martial arts were banned after World War II and, in the 1970s, was rebranded as Yamato Budogu by Mr. Ito’s father.

Mr. Ito joined the business in 1957, at age 19, and his younger brother, Tsuyoshi, came into the business a few years later. They took over the shop when their father died in 1980.

“Kendo is usually a family business,” Mr. Ito said. “I learned from my father, who was also a bogu craftsman. It’s not something you can learn at school. Some particular techniques or skills are related to certain families and handed down.”

The shop and the atelier are in Mr. Ito’s house, in the Shibuya ward, another area in southwestern Tokyo (“We used to be able to see Mount Fuji from here, but now all the buildings block the view.”). The shop, on the ground floor, is so small that two people can barely get inside: Once they slide open the front glass door, there is just a small genkan, or entry way, with bamboo swords and uniform pieces stored in glass case displays.

But when they take off their shoes, step up and walk through a doorway, there is the atelier, a large room that measures almost 900 square feet and has been outfitted with tatami mats and two long tables where the cutting and sewing are done by Mr. Ito, an apprentice and two female employees, 86 and 73, who are relatives of Mr. Ito.

Rolls of textiles, bottles of lacquers, cardboard boxes and small wooden drawers filled with tools have been crammed into any available space. Until its recent death, a large black and white cat named Fuku roamed around or napped by the gas heater.

Mr. Ito usually sits near the window on a zabuton, a Japanese floor cushion, with a blanket on his lap and a small wooden worktable nearby. Next to him is another zabuton — but that work space has been left empty for the last two years, ever since Tsuyoshi Ito died. “I wish you could have met my younger brother,” Mr. Ito said. “He was very entertaining and talkative.”

Yean Han, the 33-year-old apprentice, sits across from Mr. Ito. He is from Brunei, and had met Tsuyoshi Ito at a workshop in Malaysia in 2013. “I was already interested in how bogu is made since I was training for kendo,” he said.

When Mr. Han moved to Tokyo in 2016 to study robotics at Waseda University, his frequent visits to the atelier slowly turned into a training program.

“I became so interested and naturally I just sat here,” Mr. Han said. “Sometimes he would just throw small things at me, like ‘Try this, try that’,” he said. (Mr. Han first learned from Mr. Ito’s brother, but now Mr. Ito trains him.)

“We talk a lot sometimes. Other times he just does his work and I sit across from him for one hour or two and I just watch,” he said.

Mr. Ito seems to appreciate his apprentice: “Mr. Han is the one who welcomes customers. He speaks Japanese very well.”

Mr. Han said he was still learning skills. “I still have a certain way to go before I can be entirely responsible for making something. What Sensei will do when he creates something and thinks he can trust me with certain parts of the process, he will ask me to do one part,” he said, referring to Mr. Ito as sensei, a term of respect for someone who has attained a certain level of mastery. (He doesn’t train any longer, as Mr. Ito gave him a choice: practice kendo or make bogu.)

Mr. Ito’s handcrafted bogu is a rarity: Today, he said, less than one percent of the world’s kendo gear is made in Japan; other Asian countries, such as China and South Korea, manufacture it. Yet in the 1970s and ‘80s, when kendo was particularly popular in Japan, his shop had 14 employees and would distribute to vendors. Now it does business with individual customers.

According to Alexander Bennett, a professor of Japanese history at Kansai University and editor in chief of Kendo World magazine, “The golden age for kendo in Japan was in the 1970s and 1980s for children. There would have been a waiting list to get your child into kendo.” Now, however, the country’s low birthrate means there are fewer children, and kendo may not be as appealing as soccer or baseball.

“Kendo is traditionally known for discipline and for teaching children good manners,” he said. “But nowadays parents give their children more freedom of choice, and parents do not see the value of kendo the same way they used to.” Still, he said, the All Japan Kendo Federation estimates there are 1.5 million practitioners in Japan today; the population is around 126 million. (For comparison, there were four million to five million practitioners in the 1970s and ’80s.)

Mr. Ito is worried the old ways will disappear. “Martial arts are too ‘old school’,” he told me. “And compared to other martial arts, kendo is expensive, probably the most expensive, which could be a factor. You have to think about the costs in the long-run if your son continues kendo.”

My son’s simple cotton set and shinai, or sword, cost less than the equivalent of $100, while his teacher’s garments, bought from Mr. Ito, were around $300 and a full outfit, with shinai, can cost $500 to $1,000, depending on the quality.

But well-crafted bogu can last: Mr. Ito mentioned a client who has kept his uniform for more than 40 years. “High-quality, handcrafted items can be repaired and used for a long time,” he said as he repaired a kote, or glove, for a girls’ kendo team at a local high school. The kote was lined with deer leather, which is easily worn out and may need to be replaced as often as five times a year because the team practices daily. But Mr. Ito replaces just one small area so the team doesn’t have to keep buying new ones.

Mr. Ito’s wife, Yasuko, 79, also is part of the business: She used to take care of the deliveries, but now handles administrative tasks. “A lot of burden goes to my wife,” Mr. Ito said, and she is in charge when they all take a break for oyatsu, or afternoon snack, at 3 p.m. each workday, handing out cups of tea and sweets. “The sweet is different every day,” Mr. Han said.

Mr. Ito doesn’t take much time off. He said he doesn’t have any hobbies, but he loves the annual matsuri, a traditional festival held in September in Shinjuku, one of Tokyo’s entertainment and business districts. “If you allowed me to talk about it, I could talk about it forever,” he said.

Even though the official business hours of the shop are 10 a.m. to 7 p.m., Monday through Saturday, Mr. Ito usually works late in the atelier. “There is no end time,” he said.

“At my age, I’m often asked if I still do this as a hobby or for pleasure, but I do this to make a living,” he said. “I don’t receive any pension money like people who used to work in big companies. As a craftsman I don’t have that, so I have to keep working.”

“I’m the last bogu craftsman in Tokyo,” he said. “When I pass away, there won’t be anyone.”