Building a Fusion Power Plant in Japan: The ¥6.06 Billion Investment in Starlight Engine, and a Former-Mayor CSO on Siting and Competing Globally

The central question is this: fusion power is not expected to reach practical use until the 2030s to 2040s, so why raise money as a startup now and take on the construction of a power plant? The investor and the management each answer this from their own standpoint.

At the outset, the MC said frankly that fusion still gives the impression of something far off, still at the experimental stage. Urimoto responded that fusion is in fact a field drawing a great deal of attention right now. Japan has issued its Fusion Energy Innovation Strategy, setting out a national strategy to carry out a power generation demonstration in the 2030s.

It is tempting to think the 2030s leave plenty of time, but Urimoto says that is not the case. Advancing the design, choosing a site, building and testing will take more than ten years. If work does not start now, it will not be done in time. Companies in the supply chain and the government alike have begun moving in a big way, and Urimoto described 2026 as a turning point.

The expected application is baseload power. According to Urimoto, fully replacing nuclear or thermal power is a long way off; the aim is to deploy fusion as another power source running in parallel. It is already known that fusion can deliver generating capacity equivalent to a nuclear plant, so it could become a power source that supports society.

Growth in electricity demand is also driving this. As Urimoto explains, electricity demand had been flat in both Japan and the US. But with the arrival of AI, power consumption by GPU-based data centers is expected to keep growing at 10–20% a year, and overall energy demand across society is projected to grow by around 2% a year. Urimoto's view is that without new power sources, electricity will run short.

Starlight Engine is a subsidiary of Kyoto Fusioneering, a company that develops peripheral equipment for fusion reactors.

Urimoto described how it was founded. In 2022, an expert panel on fusion strategy was set up under the Cabinet Office's Council for Integrated Innovation Strategy. The Minister for Economic Security at the time was current Prime Minister Takaichi, and Konishi, now chairman of Kyoto Fusioneering, was invited as a member, beginning discussions on what Japan should do about fusion. In 2023, the Cabinet Office released the Fusion Energy Innovation Strategy, setting out Japan's direction of advancing fusion.

The industry association J-Fusion (the Japan Fusion Energy Council) was established, and the FAST project was launched, centered on its member companies. Kyoto Fusioneering had led FAST, but a dedicated company was needed to drive the project as its main entity. That is how Starlight Engine was spun out of Kyoto Fusioneering to carry out a power generation demonstration in Japan through FAST.

What caught the MC's attention was the makeup of the management team. The CEO spent 30 years at the trading house Mitsubishi Corporation, and CSO Azuma is the former mayor of Shijonawate. The MC had imagined a company led by researchers, but Urimoto explained that bringing fusion into society as a new industry is not just a matter of technology.

The company does have technical members, including a CTO. But gaining social acceptance and building a power plant requires collaboration with local governments, understanding from residents, and dealings with the Cabinet Office and other parts of the administration. Urimoto credits Azuma with taking on that role forcefully. The company also needs to scale up equity financing beyond subsidies, and there the CEO's connections in the business world prove powerful. Urimoto sees the team as one capable of succeeding at fundraising.

Introducing Azuma's background, Urimoto said Azuma has a science background, having researched plasma as a student, and joined the company after working at the Ministry of Foreign Affairs and in consulting. Saying there is probably no other businessperson with political experience who also understands fusion, Urimoto stated that the company had brought on the best-suited person in Japan. Azuma knows things that aren't written in books and can only be learned through hands-on experience, such as whom to consult and when, and is moving forward carefully and with great attention to detail.

On Starlight Engine's business scope, Urimoto explains that the company's founding purpose is "to build something that can generate electricity, not just stop at experiments." It will design the fusion reactor, place orders with suppliers and procure components, assemble them, and see the fusion plant through to completion. What to do with the electricity generated will likely involve collaboration with power companies.

FAST is a public-private project involving private companies and national research institutes, and it was underway before Starlight Engine was founded in April 2025. According to Urimoto, building one reactor requires about ¥800 billion, and including everything else, the cost will exceed ¥1 trillion. This round's ¥6 billion is only a tiny fraction of that. The overall conceptual design is already complete, and the project is now at the stage of estimating costs from there and moving forward.

This round raised ¥6.06 billion from 17 companies, including power companies, construction companies and trading houses. When the MC remarked that "it looks less like simply raising money and more like building a team," Urimoto agreed. The emphasis was on bringing in investors that could collaborate on the business, and negotiations were conducted to bring in not only power companies but also investors from other industries.

Power companies are especially important, and the company has been encouraging them to invest so that collaboration can begin early, including in the second close now underway. Power companies or heavy industry might be the only kinds of companies that come to mind as partners for fusion, but this time Mitsui Fudosan has also joined. That is because the siting of the fusion reactor and the development of the surrounding community will be key issues.

When the MC asked, "Is it on a scale that requires building a community?", Urimoto replied that it is envisioned as something like building a town on a large site, and that the company is thinking about deployment on a larger scale than simply putting up a power plant. Asked whether it would be something like the town Toyota is developing, Urimoto said, "It's close to that." However, Urimoto added that Azuma is in the middle of exchanging views with local governments about the details of siting, and that Urimoto personally is not familiar with the specifics. The MC took this as revealing why it matters that a former mayor serves as CSO.

The MC also raised the question of timelines. The roadmap is lined with years like 2040, while VC funds often reach the end of their term after about ten years.

Urimoto acknowledged that many funds mature after ten years and explained that under Starlight Engine's business plan, the power generation demonstration is in the 2030s and the commercial reactor in 2040, so an IPO naturally would not come in time before the fund matures. The basic premise of the investment story was therefore that the fund would exit partway through by some means.

In examining whether that story holds up, Urimoto cited three issues. The first is technology: if it isn't technically feasible, nothing can begin, so this was examined thoroughly. The second is social acceptance: whether the company can gain residents' understanding and proceed with construction. The third is future fundraising. Following this round, the company will probably raise once more next year, and after that the plan calls for raising an enormous amount of money. Whether it can pull that off was a major issue.

On this point, what Urimoto valued, in addition to conversations with the CEO, was the strength of the parent company, Kyoto Fusioneering. Through this round, it became clear that overseas investors have strong interest in Kyoto Fusioneering. Urimoto believes the next round can be raised by leveraging the connections the parent company has built. At the time of exit, fusion power should not yet be a reality, but Urimoto says the firm decided to invest having judged that this company could raise its value sufficiently.

Asked whether there is anything special about Japanese fusion, Urimoto cited its high level of technology as well as the existence of a supply chain. For ITER, an international project carried out jointly by multiple countries, Japanese heavy industry manufacturers and others have supplied components that are used in the reactor. Japan has the technology and supply chain at home, and with low energy self-sufficiency, interest in energy is high. And in 2025, the government formally declared it would pursue fusion. Based on all this, Urimoto judged that the risks mentioned earlier could be sufficiently hedged and that the company could grow.

Another important point, Urimoto said, is that fusion is included among the 17 fields of the national growth strategy. Trying to recall the figure for fusion — "I think it was about ¥3.1 trillion" — Urimoto said there is hope in the fact that the wording can be read as allowing for an increase if needed.

The MC asked whether, given the scale of ¥800 billion per reactor, this is a field that would be hard to achieve without some form of government backing. Urimoto answered as follows. It is unclear how much the subsidies will be, but raising several hundred billion yen is quite difficult given the absolute size of investment in Japan's VC market. It will be necessary to bring in overseas investors and to obtain investment from power companies and others that can collaborate. As the foundation for that, what matters for investors' decision-making is that the government shows a stance of firmly supporting this company. That stance is a bigger point than the size of the amount, and as lead investor that will also help with the next round, Urimoto wants to leverage that fact to convey the company's appeal to investors.

At the end of Part 1, the MC discussed questions for Urimoto and Azuma. The first thing Urimoto raised was where FAST's power generation demonstration reactor will be built and how the exchange of views with local governments is proceeding. During the investment review, this question came up quite often from LP companies. The other was comparison with global competitors: since Azuma had researched many companies before joining, Urimoto thought Azuma could offer a unique perspective.

The MC also suggested a pointed question: "What will you do if the expected government support doesn't come through?" Urimoto said that is naturally a possible risk as a worst-case scenario, and if it didn't come, it would mean things like the plan being delayed, but that this might steer things too far in a negative direction. Urimoto added that how to keep a lack of support from happening is a point Azuma can discuss with political figures, and asked that the MC hear about Azuma's own way of moving things forward.

Introducing themself in Part 2, Azuma said they had specialized in fusion, particularly plasma simulation, through a master's program in graduate school, and after gaining working experience, returned to the world of nuclear fusion. Azuma's career began at the Ministry of Foreign Affairs, followed by work as a consultant in India. When the MC asked whether it felt like a payoff of earlier foreshadowing, Azuma replied that this work — achieving a power generation demonstration and then a commercial plant under private-sector leadership — seemed like the place where everything they had built up so far could best be put to use.

On how siting will proceed, Azuma prefaced the answer by saying that from mayoral experience, they believe they understand to some extent what local leaders worry about and what they value. Even for something desirable and necessary for society as a whole, the question of "why put it in our municipality?" is the part that most needs explaining, including to residents.

So the company will first hold repeated exchanges of views with local governments that show enthusiasm for attracting a fusion plant and actively reach out, working through each other's concerns one by one. There are various physical conditions as well, but ultimately, Azuma says, the most important thing is to move forward together with local residents, local industry and government agencies.

Asked what residents' biggest concern is, Azuma pointed to the fact that it is an "unknown technology." Not only with fusion, but with anything humanity has never built before, anyone would feel uneasy hearing it is coming to their town. Rather than responding with "It's safe" or "Don't worry," Azuma believes the answer to those concerns is to explain carefully, as scientific fact, that certain safety measures will be taken, that there are also these risks, and that these countermeasures will be put in place for them.

The MC also asked whether the company uses "fusion" in place of "kakuyūgō" (nuclear fusion) to avoid the frightening associations of the latter word. Azuma denied this. Whether you call it kakuyūgō or fusion, the phenomenon is the same, and the company is not trying to reassure residents through naming. It simply uses the term "fusion" because it has become widespread internationally.

It is in fact an unknown technology and undeniably a technology that deals with the nuclear, so more careful answers are needed. At the same time, Azuma points out, people are routinely exposed to radiation through X-rays and the like, but for most people their feelings about that differ from how they feel about nuclear power plants, even though both are nuclear technologies. Azuma said what matters is carefully explaining in what ways fusion is similar and in what ways it is completely different.

On the response from the local governments the company has already begun communicating with, Azuma explained as follows. Building a fusion plant also requires the strength of surrounding industries, so many local governments are interested in the economic effects. Industry departments and business attraction departments tend to be relatively positive and eager to hear more. Meanwhile, departments that take a broader view, such as crisis management, ask what risks there are. At the current stage, each part of the same local government is functioning according to its role.

Showing a model of FAST, Azuma explained the size of the device. In the fusion world, it is common to express a device's size by its major radius, and FAST's is about 4 m from the center. Overall, one can picture it as being around 20 m.

Compared with other devices, among tokamaks, it is larger than the physics demonstration device that Commonwealth Fusion Systems in the US is building. On the other hand, ITER, the tokamak experimental device being built in France through global cooperation, has a major radius of over 6 m, so FAST is smaller than that.

According to Azuma, there is a reason for this size. A tokamak is a structure with many coils arranged in a circle; making it smaller makes the design of the central part difficult and increases the technical challenge of confining high energy in a narrow space. SPARC in the US is taking on that challenge. Conversely, the bigger it is, the more time and cost construction takes, and the harder it becomes to make it commercially viable. Azuma explained that FAST settled on this size with a focus on feasibility, taking everything into account, including incorporating American-style technological innovation in high-temperature superconducting magnets and making it commercially viable.

The actual facility will further enclose the device in a containment vessel, so from the outside it will be a large building of about 50 m. FAST is strictly a power generation demonstration plant, not a device that supplies electricity to homes. Beyond it lies the commercial reactor; various output designs are possible, but its output will be equivalent to a thermal or large nuclear plant. So it is not something to be lined up in countless numbers like solar panels. Like a thermal power station, combinations such as placing multiple units on one site and running the others while one is under inspection are possible, Azuma said.

On Urimoto's description of it as "like building a whole town," Azuma responded, "Exactly." Including costs, it will be on the scale of about ¥1 trillion. Jobs will be created, and if researchers gather, it may become necessary to develop an environment for their families and children's education. Building roads to transport construction materials improves the living environment, and commercial facilities may follow. It is close to the sense of building an ecosystem around it.

When the MC cited the example of hourly wages rising around TSMC's plant in Kumamoto, Azuma replied that they want to factor in such effects from the outset and think in terms of linking them to benefits for the whole region. However, rather than the company taking the lead, Azuma hopes local governments that are always thinking 5, 10 or 20 years ahead will see it as one tool.

On siting conditions, Azuma said there is no place in particular where "it has to be here." To take it to the extreme, even in the mountains it would not be technically impossible, though it would cost more. A coastal site has advantages such as being able to use seawater, but securing cooling water is not essential as it is for nuclear power plants, so one can't generalize. That said, given that it is a baseload power source unaffected by natural conditions, a green power source, and high-output, it would make a good partner for regions with electricity demand now or expected in the future.

Asked whether one could be built in Tokyo, Azuma answered, "Of course." Tokyo uses the most electricity, and going forward, data centers near cities will inevitably be needed, because distance causes latency issues. If large-scale power infrastructure is what drives industrial and international competitiveness, a future is possible in which the countries that move quickly to build data centers near cities and the fusion to support them will be the ones that gain competitiveness, Azuma says. However, for AI training, being near a city isn't necessary, and there is also the option of combining solar and other sources. Since this is energy policy, Azuma said, a process is needed to envision the ideal shape while assessing things across the country as a whole, rather than confining it to a single area.

On the position of Japan's fusion industry, Azuma first emphasized its accumulated science and technology. In plasma science — burning plasma to induce fusion reactions — Japan can be said to have been at the forefront of the world. Naka City in Ibaraki Prefecture is home to JT-60SA, the world's largest tokamak experimental device. On the industrial side as well, Japanese companies have supplied major components for ITER.

But according to Azuma, the field is now entering a phase where the private sector must also invest in giant projects like FAST. What becomes important there is predictability of funding; without predictability, no one can invest. In the US, private capital is actively moving and an ecosystem has formed, while China is moving through the power of the state. Japan has won in plasma science, but it is at the stage of deciding as a country to "go with this," funding predictability is not yet settled, and industry is only just getting off the ground. That is precisely why FAST raising its hand and saying "Everyone, join in" and moving forward will strengthen the industry. Azuma positioned this as the main purpose of the company's business.

The lineup of investors in this round reflects that thinking. In addition to representatives of supply chain companies, the company brought in companies that are electricity consumers and companies with a community-development perspective. Azuma says fusion is not just about generating and selling electricity, and the investors may have invested with the shared aspiration of making it a growth industry for Japan across sectors.

On government support, Azuma said Japan takes energy seriously and sees fusion as a power source with future potential. When a nation builds a portfolio of power sources, it is natural to think separately about what can generate electricity right now and what will be needed ten years from now, and in light of a roadmap with such timelines, Azuma considers current support to be relatively solid.

Asked whether political stability is important for a long-term undertaking, Azuma said it is not irrelevant but does not think it applies to fusion. The basis Azuma cited is ITER. There is probably no other example of countries with clearly different agendas — the US, Russia, China, Europe, Japan, India and others — continuing the same project for so long. Azuma believes it continues because fusion is probably the ultimate destination for humanity's energy, and humanity is trying to invest money toward that goal. In Japan, low energy self-sufficiency is a problem that needs solving, and the argument that solving the energy problem over the medium to long term is good for the entire nation would not be rejected by any administration or school of thought. Azuma added that support from the administration is appreciated, but rather than relying only on a particular administration, it is also necessary to explain things broadly and carefully to government officials and members of the Diet.

Asked what Japan needs to get a step ahead of other countries, Azuma answered that precisely because Japan is competing with other countries, the first thing is how the domestic side can come together with a shared vision and strategy. Japanese fusion research has a broad base, with a history of researchers publishing papers in many fields, and compared with the US and China, many people have been involved for a long time. Among them, there are also differences in thinking. The breadth of the base is wonderful in itself, but at the industrial policy stage of who will be first to achieve a power generation demonstration, set the standards and expand globally, selection and concentration become necessary. Azuma explained that Japan does not yet have a settled direction, and the government's current thinking is to work that out.

As for other countries, Azuma says China's strategy is very easy to understand. The US and Europe are trying to form a supply chain with like-minded countries including Japan, but China is going it alone, strategically advancing device development so that it can build on its own CFETR, a tokamak reactor regarded as the final form, even if it takes time. Azuma called this a skillful strategy and said that even from the outside, one can sense an unwavering national will. The US, meanwhile, is pursuing development led by the private sector, building plants and signing power contracts. Azuma's impression is that its capital markets are its defining feature and companies are crafting strategies and tactics to match. The MC offered a personal impression that this resembles the structure of the battle for platform dominance, in which the US expanded globally and China built its own rival camp.

What Azuma aims for is for Japan to go after the Tier 1 position — that is, the integrator. If Japan leads in plasma science and has strengths in Japanese companies' manufacturing capabilities, engineering and materials industries, Azuma believes this is possible in fusion. As things stand, Japan risks remaining a country that merely supplies excellent materials and components to the US and China, which are good at securing such positions. To prevent that, Azuma said, this is the moment for Starlight Engine to act as the overall coordinator and take responsibility for moving things forward, including the supply chain.

Finally, the MC asked how viewers who have experienced frustration over the past 30 years should view and support the fusion industry. Azuma acknowledged that being told energy is produced when light atomic nuclei fuse together sounds like something from the distant future, but said it is what happens in the sun we see every day. No one has negative feelings about the sun. In space there is no air or oxygen, and no one is adding firewood, yet the sun keeps burning and giving us its blessings. Fusion is the effort to create that, through science and technology, by human hands in a place close to us, and Azuma said that hearing this as a child, they strongly felt, "That's right."

With an energy source that keeps burning, society would have the electricity it needs without worrying about oil imports, uranium procurement, solar on cloudy days or wind power on windless days. Azuma sees the fusion plant as an important device for viewers and their children to have a peaceful future. Azuma's closing words were that they would be glad if people saw it not as an unknown technology, but as a technology that brings a phenomenon we see every day down to Earth.