Why Love the Konjac-Based Organs from Saitama?
A small Saitama factory turned adversity into innovation by creating plant-based simulated organs out of konjac for surgical training.
The products are gaining traction globally.
If people outside of Japan have heard of konjac, it is as an alternative to potatoes. The Japanese often refer to the plant as konnyaku and use it widely in a variety of dishes, especially oden.
You may have encountered oden on a visit to a convenience store in autumn or winter, where the different ingredients simmer away next to the counter. Konnyaku is the grey, gelatinous substance with black spots. It’s better than that description, and, according to some, excels because it has almost no calories.
For Kotobuki Medical, in the small, sleepy town of Yashio in Saitama Prefecture, it was a very different quality that attracted them to konnyaku: its consistency.
Through a lengthy development process, the company created its Versatile Training Tissue (VTT), primarily made from konjac flour, providing surgeons with a remarkably realistic substitute for human tissue.
From toy tires to tragedy to lightbulb
Kotobuki’s history begins in the world of toys. Founded over 40 years ago by Shunju Takayama in Adachi, Tokyo, the company was known as Kotobuki Giken, a subcontracting factory that produced small components.
Over time, the company shifted its focus to other types of products, partly due to a series of unfortunate events, culminating in the 2008 Lehman Shock, which drained what little resilience remained.
The idea for the move toward medical equipment and konnyaku tissue came from a chance meeting between the younger Takayama, Seiichiro, and a childhood friend who worked for a major medical device manufacturer.
In the early 2010s, laparoscopic surgery was becoming more common, but doctors had no proper way to train.
Professional training kits cost upwards of ¥400,000, far beyond the budget of most hospitals or medical students. Takayama realised that if Kotobuki could produce a high-quality training box for ¥20,000–30,000, it would transform the field. Using the factory’s precision machining experience, he developed prototypes, interviewing surgeons along the way. The result was a low-cost laparoscopic training box, which turned out to be an instant hit.
From mock liver to medical breakthrough
In 2012, Japan banned raw liver consumption after food poisoning cases. Food scientists began producing konjac imitations of liver for restaurants. The Takayama team took notice. If konjac could imitate meat in texture, why not organs?
It turned out to be a simple question with a complicated answer, but Seiichiro was convinced he was onto something. Beginning in 2015, he and the company spent two years of intense experimentation, producing more than 1,000 prototypes, before unveiling the first konjac-derived simulated organ.
The timing turned out to be perfect. Traditional models made from silicone or plastic were expensive, lacked realism, and posed environmental problems. Animal tissue, sometimes used in training, was ethically fraught and inconsistent. VTT offered a plant-based, sustainable, and realistic alternative.
From local factory to global player
From a start in the home market, Kotobuki soon expanded oversea, including a deal with Johnson & Johnson.
Exhibitions became key stages for winning doctors’ trust. As President Takayama put it, “By looking beyond Japan, we could enjoy economies of scale. Our goal has always been to manufacture for the world.”
Recognition soon followed. In 2023, Kotobuki won the Forbes Japan Healthcare Creation Award, cementing its reputation as one of Japan’s most promising medical innovators.
Why konjac works
Konjac might seem like an odd choice for surgical organs, but its flour can be moulded and layered, creating membranes and textures that mimic human anatomy. Unlike silicone, it’s biodegradable and environmentally friendly. Unlike animal tissue, it’s safe, consistent, and free from ethical complications.
For practising surgeons, the product provides a close similarity with human tissue, including when a scalpel slices into it, how simulated vessels can be cauterised, and even the lifelike feel when sutures are tied.
Kotobuki isn’t stopping at gallbladders and lungs. Its roadmap is ambitious: replicate all major human organs, complete with bleeding mechanisms and simulated lesions. The goal is not only to provide training but to allow device makers to test tools in controlled, realistic conditions.