On weekdays, Hiromi Arai is an electrical engineer. But when the weekend arrives he dons an apron and spends hours making soba noodles.
Arai is among an increasing number of Japanese of all ages taking a new interest in soba, traditional buckwheat noodles that have been around for more than 1,000 years.
Riding to new heights of popularity as a health food, the earthy noodles are also getting a boost from gourmets, who have set up a course training people to appreciate the finest noodle nuances, much as sommeliers learn about wine.
Enthusiasts like Arai, 44, have a far simpler explanation for their passion.
"I just really like to eat soba," he said.
"Besides, soba is deep. You make it out of only flour and water, but the flavor can change completely depending on how you roll it and on the flour," he added.
"The more you know, the more there is to know."
Arai, who has studied soba making for two years, brings his own cherished soba-rolling stick to classes at the Tsukiji Soba Academy.
Soba, made of buckwheat flour and water, with wheat flour or sometimes egg added, apparently came to Japan from China by way of Korea. Mentions of it were made as early as the 700s AD.
It wasn't until the 1600s, however, when Tokyo became the centre of Japan's government, that soba began to become popular by playing a role in the social life of the rising merchant class, said Akira Inoue, head of the Tsukiji academy.
"In those days, soba wasn't a meal but more like going out for coffee or a cocktail with friends," he added.
Aficionados say the best type of soba is the simplest: cold noodles dipped into a soy-flavored soup, garnished only with chopped scallions and a bit of wasabi horseradish. Slurping is required to savor the flavor best.
Though soba shops have long been an ubiquitous part of Japanese towns, they were seen mainly as the territory of middle-aged men until recently.
But increasingly health-conscious Japanese have had their eyes opened to soba, which proponents say contains protein, essential amino acids and, best of all, few calories.
Soba, thanks to buckwheat, also contains rutin, a compound believed to help reduce blood pressure and strengthen blood vessels and may have anti-cancer and anti-ageing properties.
"We've seen a lot of young women and young men getting into soba over the last few years," said Inoue. "Everyone is thinking about their health and there's absolutely no fat in soba."
Another factor behind the boom is that soba is easy to make at home, further fuelling the passion of many devotees as they work to make the perfect soba noodle - and soup - themselves.
Among them are the handful of men who gathered at the Tsukiji Soba Academy, near Tokyo's fish market, on a recent Sunday.
Wearing aprons, with bandannas on their heads, the students pressed close as Inoue demonstrated how to knead, roll and cut soba before trying the techniques for themselves.
Amid the rustle of sifting flour, grunts of effort and exclamations like "Whoops, I just did that backwards," the six men prepared and then sampled soba under walls hung with racks of metre-long rolling sticks mounted proudly like samurai swords.
"I don't do any other cooking," said Toshio Matsuda, who works in an architectural firm. "But it's fun to make my own soba, have my friends over and serve it to them."
The truly passionate can choose to take a separate course at Kanda Zatsugaku University, a non-profit night school, that will earn them a certificate as a "sobalier", or soba sommelier.
Studies begin with lectures on soba and the culture that surrounds it, then continue with soba making. After this, students survey a minimum of 10 soba restaurants and write a report.
Finally, they write a thesis. If this is accepted, they become "sobaliers" at a pomp-laden ceremonial dinner.
"It's a good chance for everyone interested in soba to exchange opinions," said founder Ichiro Suzuki. "Walking around and tasting is the main part."
In the three years the course has been running, 1,000 people - from a junior high student to people in their late 70s - have graduated.
"I did it all in the spirit of fun, but looking back on it, writing the thesis and the reports was kind of hard," said Junko Nishiwaki, who was interested in the health benefits of soba before becoming a sobalier in 2004.
Even so, the 32-year-old, who works in finance, said there are limits to her passion.
"I'm not really interested in making soba," she said. "Eating is my speciality."