The useful thing about a basement is that it refuses to flatter you. In 2015, beneath Seoul's Yongsan Electronics Market, Sunjong Ryu and his co-founders had no panoramic view, no ceremonial lobby, and no reason to mistake atmosphere for progress. They had pooled 10 million won each from their severance pay. Around them sat the unromantic ingredients of hardware: parts, tools, technicians, loading docks, and the knowledge that anything physical eventually has to survive contact with a factory.
They named the company N15 after Najin Building 15, the place where they began. It was both a postal fact and a small act of discipline. A startup name usually strains toward tomorrow. This one kept pointing back downstairs.
Najin Building 15 · Yongsan Electronics Market · 2015. An address became a company name, and a neglected commercial district became raw material.
Ryu did not arrive as a romantic tinkerer untouched by office life. He had worked at Woori Bank and an LG affiliate. He had also started a military-goods online shop called Gunbari365. Then came an Information and Media MBA at KAIST. During a Silicon Valley entrepreneurship project, he and classmates met dozens of founders and investors. The encounters rearranged the ambition he had carried into graduate school. The goal, as he later put it, moved from finding a better-paying job to creating value through a company.
A shop floor for the missing middle
Software can travel from laptop to user before lunch. Hardware is less obliging. It needs a casing that closes, a circuit that behaves, a supplier who answers, and a manufacturing line that can reproduce what the prototype promised. In 2016, N15's founders described the ordeal as a one-to-two-year path just to reach a prototype. Ryu and his partners saw a business in shortening that path.
Yongsan was an inspired place to attempt it. The district had lost some of its old status as Korea's electronics mecca, but it still held dense practical knowledge. N15 connected that knowledge to 3D printers, workspace, startup programs, investors, and larger companies looking for new ideas. In 2016, the company helped create Seoul Digital Blacksmith, a public manufacturing space. By 2017, N15 had incubated roughly 60 manufacturing startups and invested directly in 10.
“N15's goal is to build an open-innovation platform connecting startups with technology and large companies with capital.”Sunjong Ryu, 2016
The 3D printers made the photographs. The connections made the company. Intel, LG, Samsung, and Nissan's Infiniti were among the corporations reported to have approached N15 for prototyping or open-innovation work. In 2017, Bouygues chairman Martin Bouygues visited the Yongsan operation to discuss collaboration. N15 had positioned itself between groups that wanted one another but spoke different operating dialects.
Ryu eventually gave that role a pleasingly ordinary name. N15 wanted to act as a product manager for startups and small businesses. By 2019, his plan stretched from prototype to contract manufacturing and sales. The company was mapping factory information in Korea, Shenzhen, and Ho Chi Minh City, while looking toward crowdfunding in Japan and distribution in the United States. The ambition was not merely to make an object. It was to carry the object through every handoff where it could quietly die.
Founder arithmetic
Four months after N15 began, Ryu published a short essay about the pleasure of starting a company. Friends kept asking whether he preferred it to corporate work. His answer was crisp: startup life was 10 times busier and 20 times more enjoyable. He was handling at least five jobs. The multiplication of effort was obvious. The multiplication of enjoyment came from making his own decisions.
Ryu's 2015 founder equation was not a productivity claim. It was an argument about agency: more roles, more responsibility, and more say over what happens next.
This is not the breezy freedom sold in entrepreneurship posters. Agency comes with the bill attached. A founder can choose the direction, and then has to face what the customer, payroll, production run, and balance sheet think of the choice. Ryu's fondness for execution seems to begin there. Ideas are pleasant company. Decisions reveal whether they can work.
His view of people is similarly reciprocal. In a 2022 KAIST interview, Ryu said that people ultimately make everything happen. For a startup trying to earn trust without the resources of a conglomerate, he pointed to flexible schedules, remote work, workations, and faster links between performance and compensation. The aim was not blind faith in employees. It was to make the company and its crew dependable to one another.
The donation carried a neat symmetry. Ryu gave KAIST 10 million won, the same amount he said each founder had used to start N15. He credited the MBA with changing him from a person receiving a salary to one responsible for paying salaries. His advice to would-be founders was admirably small: build the product or service you want at minimum cost, then see whether an actual customer will pay. A modest paid test, not an elaborate declaration, is the useful unit of courage.
After the accelerator
N15 kept widening. A separate accelerator, N15 Partners, was established in 2018. In 2020, N15 raised 3 billion won from Lotte Accelerator and Arcane Investment. Its work extended across investment, manufacturing, commerce, training, and corporate programs. That range might sound unruly until you see the same question hiding inside each piece: what is stopping this promising thing from becoming a functioning business?
In 2023, Ryu completed the sale of N15 Partners. The exit did not send him away from operating problems. It changed their scale. At In & Out Corporation, he began concentrating on brands that could make a product but had reached what he calls a growth ceiling. Strategy was plentiful. The machinery linking product, marketing, distribution, revenue, and profit was not.
The response is called Brand OS, an operating system for a portfolio of businesses. In & Out says it diagnoses the business, helps structure funding, develops private-label products, builds content and channels, supports franchising and business-to-business distribution, and can stay through an eventual exit. Its announced portfolio spans food, retail, interiors, and hospitality concepts. The vocabulary has moved far from maker spaces, but the job remains recognizable. Find the handoff where progress stalls. Build across it.
“A company's value comes not from the size of its investment, but from the sales and profit of services and products that customers repeatedly seek.”Sunjong Ryu, 2026
There is a quiet correction to startup culture in that sentence. Funding is useful, sometimes essential, and N15 itself raised it. Yet money arriving from an investor and money arriving from a returning customer answer different questions. One recognizes possibility. The other recognizes a habit worth repeating. Ryu's latest chapter puts the second answer near the center.
What builders can steal
First, inspect old infrastructure before demanding new infrastructure. Yongsan's fading reputation concealed a live network of parts, expertise, and proximity. N15 did not need to invent those atoms. It needed to give them a new arrangement.
Second, follow the failure point. When prototypes could not reach production, N15 built manufacturing links. When manufactured products lacked distribution, it moved toward commerce. When brands could not turn attention into recurring economics, In & Out widened the system again. Expansion for its own sake creates clutter. Expansion around a repeated blockage creates a spine.
Third, keep the first test small enough to tell the truth. Ryu's counsel to students was not to wait for graduation, a perfect deck, or an office worthy of photography. Make the cheapest credible version. Ask someone to pay. Every founder would prefer a grand verdict. A small transaction is usually more informative.
The N15 basement matters because it makes those lessons physical. It was located in a market caught between former glory and uncertain reinvention. It had fewer comforts than a corporate office and more useful friction. Ryu walked into that setting after banking, LG, an earlier online shop, and business school. He did not discover that ideas were rare. He discovered that the path from idea to object was badly furnished.
A decade later, the furniture has changed. The object may be a restaurant brand or a retail concept rather than a circuit board. The scoreboard may be repeat purchasing and operating profit rather than the number of prototypes. But Ryu is still working in the basement, metaphorically speaking: the place below the attractive surface where supply, people, money, and decisions have to fit. It is busier down there. By his arithmetic, that may be the point.