In Yamanashi Prefecture, there is a tradition of aerial fireworks known as "Koshu Fireworks," which has passed down traditional techniques for generations.

Tracing its roots back to the smoke signal guards of Kofu Castle, Yamauchi Fireworks Co., Ltd. has been crafting fireworks for over 150 years. It is a long-established fireworks manufacturer that continues to make a name for itself nationwide, including winning the prestigious Prime Minister's Award at the Omagari National Fireworks Competition.

Behind the iconic summer tradition that colors Japanese skies lies the painstaking daily craftsmanship of dedicated artisans. We spoke with Yuichi Yamauchi, a young fifth-generation pyrotechnician, about the techniques and passion passed down through generations of fireworks craftsmen.

Koshu Fireworks: Rooted in Kofu Castle's Smoke Signal Guards

Along the Fruit Line, a scenic road passing through Yamanashi's famous orchard belt of grapes and peaches, lies Mount Kabuto—one of the 100 Famous Mountains of Yamanashi. Deep in these mountains stands the Kasugai Factory of Yamauchi Fireworks, where Koshu Fireworks continue to be made. Climbing the mountain trail to the factory, we were greeted by fifth-generation pyrotechnician Yuichi Yamauchi, who had prepared old historical documents related to Koshu Fireworks.

"Koshu Fireworks were officially designated as a Yamanashi Local Traditional Craft in 2023. To get that designation, I spent time researching old documents about fireworks makers across the prefecture and interviewing many people," Yamauchi shares.

Yamauchi Fireworks was founded in 1868 (Meiji 1). The oldest surviving record of modern aerial fireworks in Yamanashi Prefecture dates back to a fireworks display held in 1873.

"A program for that fireworks display, distributed as a supplement by the newspaper company that preceded the Yamanashi Nichinichi Shimbun, still exists today. In those days, local notables would buy fireworks shells and have them launched under their own names. On the program, there are self-evaluations of the shells, presumably written by the company's founder," he explains.

The roots of Koshu Fireworks are deeply tied to Takeda Shingen, the famous warlord who ruled this region. The ancestors of Yamauchi Fireworks originally served as smoke signal guards at Kofu Castle, handling signal fires and gunpowder.

"An initiation certificate for Asahi-ryu Kajutsu (pyrotechnics), the art of handling gunpowder and smoke signals, still remains. It seems there were also oiled paper umbrellas and castle entry permits used for official duties, though those were sold during the war. From pyrotechnicians skilled in handling gunpowder, the first-generation Sojiro started what is now Yamauchi Fireworks," Yamauchi says.

In the Meiji period, national laws regulating explosives were enacted. Records show that Yamauchi Fireworks became the first in Yamanashi Prefecture to obtain a fireworks manufacturing permit under these laws. Yamauchi is a true craftsman carrying these long-standing traditional techniques into the present day.

"There are three companies in the Yamanashi Traditional Fireworks Association. Among them, Yamauchi Fireworks is the only one that has continuously crafted impressive 2-shaku (approx. 60 cm) fireworks shells. The 2-shaku shell is extremely unforgiving; without advanced skills, there's a high risk of failure, such as premature detonation or low-altitude burst," Yamauchi explains.

Naturally Inheriting a Family Business Dating Back to the Meiji Era

Born into a family of fireworks artisans, Yamauchi helped out with fireworks production little by little during his university days, taking advantage of summer and winter breaks.

When asked, "When did you decide to take over the family business?" Yamauchi paused for a moment to think before replying, "It just happened naturally."

"Part of it might be that there were too many geniuses around me. In middle and high school, my classmates were so smart that I felt I stood no chance competing against them head-on.

"On the other hand, with fireworks—which I had watched since I was a child—I felt I could pour my own ideas and ambitions into a single piece of work and aim for the top. Whatever I do, I want to be number one."

At university, he studied applied chemistry. He chose this field because it offered exemptions from various subjects when acquiring the qualifications necessary to manage a fireworks company.

"Studying chemistry helped me understand what is essential when blending raw materials based on their physical properties. For example, if something doesn't ignite well, instead of blindly tweaking the gunpowder ratio, I can approach the issue by understanding the underlying principles. That was definitely a plus."

When Yamauchi was a student, the previous generation head, Hiroyuki, was making remarkable strides. In 2012, he won the Prime Minister's Award at the "大曲全国花火競技大会", where pyrotechnicians from across Japan compete. In 2017, he set off fireworks at the "国際花火シンポジウム", an event gathering pyrotechnic professionals from 37 regions worldwide.

"The day after we set off our fireworks, a launch ignition equipment vendor from Germany I had met before told me, 'I've never seen fireworks like that before—it was amazing!' That was a huge source of pride and inspired me to pursue this path."

Creating a Beautiful Circle Is the Hardest Part

Let's take a look at the traditional fireworks crafting techniques handed down through generations. Yamauchi Pyrotechnics' facility is built on a mountain slope, efficiently designed so that the process begins at the top of the hill and moves downward as work progresses. In Yamanashi, finding flat land for factories is difficult, so many facilities are built in the mountains.

First, in the mixing room, oxidizers and fuels are combined to create the gunpowder that forms the base of the colors. The process of building up the stars—alternately coating 3 mm cores with a liquid gunpowder mixture called "toro" and dry gunpowder dust to gradually enlarge them—is known as "hoshigake" (star coating). The loud clatter of rotating a large tub to mix them resonates pleasantly.

"If there is too much or too little toro, it won't work. Since temperature affects it too, getting a feel for the concentration and amount of toro is crucial. You can actually tell the current state of the stars by the sound of the rotating tub. If I feel there's not enough powder, I sprinkle more in and spin the tub again."

After repeated rounds of star-coating and sun-drying, the enlarged stars are packed into shells by hand.

"If there are gaps between the stars, that section will lose its color when launched. Even the Japanese paper placed between layers of gunpowder must be neatly folded so the wrinkles are uniform. In fireworks craftsmanship, consistency in everything is essential."

"A lot of the work is unglamorous," Yamauchi says. Even if every step is performed meticulously, there is no guarantee the shell will open beautifully in the sky.

"Even if you make two fireworks using the exact same stars and bursting charge, they will never open identically when launched. In the end, there are things you can't know until you actually fire them. When it comes to fireworks, creating a perfect, beautiful circle is the hardest part of all."

Launching Fireworks Safely and Efficiently

A pyrotechnician's job doesn't end with crafting fireworks; launching them into the night sky is just as vital. Amid hectic daily routines, safety remains the top priority to ensure flawless, beautiful displays. To achieve this, preparation is everything.

"During preparation, even the smallest detail can determine whether every single shell launches cleanly without leaving any behind. If you pack up your tools neatly when finished, you can move on to the next site without losing time. Working efficiently and always thinking ahead is truly essential."

On-site, technicians must also be ready for unexpected situations. While rare, if an electronically controlled launch fails, they must grab a protective shield and manually ignite the fireworks themselves.

"A firework failing to launch is the absolute worst outcome, so we must get it into the sky no matter what. Safe execution requires comprehensive experience and technical skill. Saying 'We couldn't launch it' simply isn't an option for a professional firework company."

Even with years of experience, the moment of launch is always nerve-wracking, leaving them wondering if everything was done perfectly. Yet, the audience's reaction after a successful show makes all the hard work worthwhile.

"After the fireworks go off, the crowd's cheers reach us all the way at the launch site. Getting a direct reaction to something you created—I don't think there are many jobs quite like this."

Even a Lifetime May Not Be Enough to Create a Truly Satisfying Shell

With awards from national competitions, the name Yamauchi Fireworks Co., Ltd. is known across Japan. At "Omagari Fireworks: Spring Chapter〜New Fireworks Collection 2026〜", they launched a shell titled "The Night Parade of a Hundred Demons: An Encounter with the Unknown" and claimed victory in the New Fireworks Category.

"I watched the Netflix drama "Stranger Things: The Unknown World" and wondered if I could express that eerie atmosphere through fireworks. I wanted to turn that terrifying feeling of an uncanny, threatening presence drawing near into a firework."

Yamauchi says that being able to express his ideas in front of hundreds of thousands of people is what makes being a pyrotechnician so captivating. When asked about his future goals, the craftsman, who continuously sharpens his skills, shared his vision:

"To create a shell that I'm truly satisfied with. Right now, I'd say I'm only at about 80 percent. Finding flaws is endless—wishing I'd waited a few more seconds before transitioning to the next color, for instance. I feel like even if it takes my entire lifetime, making just two or three truly satisfying shells would be enough."

Beyond technical craft, there are various obstacles, such as raw materials becoming unavailable due to suspended orders and shortages of the traditional handmade Japanese paper (washi) required during shell loading. While Yamauchi Fireworks has welcomed younger artisans, many peers in the industry are forced to close down due to a lack of successors.

"Despite these challenges, our primary goal must be increasing the number of craftspeople. Every day, I keep searching for ways to share my work with others. Beyond that, it's about crafting things with our own hands. At the end of the day, steadily honing our skills is what matters most."

Fireworks lighting up the summer night sky—every fleeting moment is packed with painstaking artistry and tradition passed down through generations. Keeping this in mind will make watching this year's fireworks display even more special. So let's cheer loudly, loud enough for the artisans to hear.