Hidden Wonders | Japan's Last Silkworm Farmers

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Gunma Prefecture remains one of Japan's leading sericulture regions, producing around 40% of the country's cocoons. It is home to Tomioka Silk Mill, a UNESCO World Heritage site.

Hiroo Asai, a farmer in Tomioka City, moved into the home of a former sericulture farmer and now raises silkworms there.

Each year, Asai begins raising silkworms in May. After hatching, they feed continuously on mulberry leaves and begin spinning cocoons after about 25 days. At that point, they are transferred to a rotating cocooning frame (mabushi), a tool lined with small compartments where they spin their cocoons.

*Hiroo Asai checks silkworms in the rotating cocooning frames.*

Asai raises silkworms five times between spring and autumn, shipping about 800 kilograms of cocoons each year. The cocoons are then sent to a silk-reeling factory, where they are spun into domestically produced raw silk.

Asai first encountered sericulture in his twenties. He was inspired by a mentor during his training who cared for silkworms using all five senses.

*Asai harvests mulberry leaves for his silkworms, then quickly carries them to the rearing house so they can be fed while still fresh.*

Using his entire body, Asai judges their health and stage of development. He listens to the sound of silkworms eating mulberry leaves, observes their body color, feels their firmness, and even smells their urine. Asai says the appeal of sericulture is that "the harder you work, the bigger the cocoons the silkworms produce."

Watch scenes from the silkworm farm

A Declining Industry

Raw silk, once a major export that supported Japan's economy, entered a period of decline after reaching its postwar peak in the 1960s, as domestic producers struggled to compete with lower-priced imports.

*The Tomioka Silk Mill, designated a UNESCO World Heritage Site in 2014. Exhibits inside trace the history of Japan's silk industry.*

The number of sericulture farmers in Japan has continued to fall. According to the Dainippon Silk Foundation, only 113 farms remained as of 2025. About two-thirds of the farmers are aged 70 or older, and most have no successor.

At a forum of silk industry stakeholders held in March, participants voiced concerns that Japan's silk industry could disappear within five to 10 years. They called for ways to encourage consumers to choose products made with domestically produced raw silk.

*A silkworm feeding on mulberry leaves | Silk-reeling machines at the Tomioka Silk Mill, preserved as they were when operations ceased*

Growing the Community

"It's a declining industry, but I also see its potential," Asai says. He now accepts trainees hoping to enter sericulture and looks toward the future of the traditional industry. "I want to increase the number of people involved in our production region and ship more high-quality cocoons."

*The cocoons are shipped about seven days after they are spun. By autumn, Asai completes five rearing cycles and raises around 450,000 silkworms in total.*

Silkworms once helped make Japan prosperous. Domestically produced raw silk is still used in the Shikinen Sengu, the periodic rebuilding of the shrines and renewal of the sacred garments at Ise Grand Shrine. The silk industry, deeply intertwined with Japanese culture, now faces a critical moment.