Mitsuo Sasaki (76 years old)
Born in 1945

1-14-5-705 Higashihoncho, Koga City, Ibaraki Prefecture, JAPAN

Place of Birth
Tsugaru City, Aomori Prefecture

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When you throw a stone on the surface of the water
Ripples arise, expanding circles to a big area
When you throw a stone named Mugen on the calm sea Orange circles spread all over the world



Established the construction company ,”Tsugaru Souken”


Although he grew up the company to be a top construction company in Yamato City near Tokyo, he was disgusted by the old-fashioned business format of the construction industry, such as collusion and turf wars, and sought a business that could fully demonstrate his abilities. As a result, he broke up with the construction industry, which is an order-taking industry, and found a cause in seeking to transform into a product sales company that makes most of his creativity.


Construction Site


Tsugaru Souken Head Office Bldg


Despite his understanding the risk of changing the business format, He decided to take on the challenge boldly, named the company “Just Japan”, opened its head office in Sibuya-ku, Tokyo and started the sales business with products represented by the following three original items:

  • Steel-based multi-storey car park, “Just Park
  • Three-dimensional bicycle parking lot made of steel, “Just Unit
  • Fence product made of plastic, “Just Guard

Mounted multi-story car park “Just Park”Prototype experimental body


Just Unit Prototype experimental body


Just Guard Fence

The above three items in the photos turned out to be timely products to deal with the shortage of parking lots and other spaces. Sales jumped up to 4 billion Japanese yen in the first year, 10 billion yen in the second year, and reached 30 billion yen in the fifth year. We were proud that we had contributed to society by introducing a blockbuster product in the early days of multi-story car parks that we see as a matter of course in big cities today.


Just Park under installation


Some other example


Just Park installed in a local city


Just Park installed in the city center


Just Park installed in a supermarket


Obtained a patent for the stationary multi-story car park “Just Park” and started selling it as a stationary steel shelf because it can be used by placing it on the land without fixing it to the land (foundation work). Although sales were very strong, the invention was one that could not be legally regulated at the time. The relevant ministries and agencies in Japan worked together to exert a huge pressure by all means to thoroughly stop our business. Since the company decided not to rely on any political power to cope with such problem of ours, it eventually went bankrupt.



Mitsuo Sasaki was involved in a traffic accident on the highway and lost his left leg from his thigh. After about one year of his fight against such severe injuries, he became to be a handicapped person despite his rehabilitation effort.

Precast concrete multi-story park planned while he was in a hospital and wanted to kill time.


Moved to Thailand for a warm climate in consideration of his health.


Received an order for the concrete wall structure “Mecha House” in Thailand. We undertook the design and construction of warehouses and factories on a site area of 30,000 ㎡


Precast Concrete wall structure “Mecha House” panoramic view


Photo under construction


Photo under construction


P.C. Concrete wall structure “Mecha House” half view


Developed and designed rooftop waterproofing equipment for precast concrete structures and obtained patents in Japan, Indonesia, and Thailand.


Returned to Japan due to epidemic of Covid-19 in Thailand. Now he spends his days thinking about miscellaneous ideas as his hobby, while living a comfortable life.

What is inventing? (In the case of Mitsuo Sasaki)


He thinks it is important to find a theme that should be invented in everyday life. For example, suppose you want to create a monument of a simple and beautiful pyramid as a motif. Think about what kind of shape, size, material, cost, usage, etc., would be good, while living a normal daily life instead of sitting at the desk all the time.

When the outline of various ideas is organized to some extent, he will consider the design and features concretely. Think about whether the monument is fixed to the land, whether it can be transported by truck, or ship, and so on. Once he has thought up a certain outline of the monument, he will start working on the details. In other words, he thinks deeply about how to make the target product faster, cheaper, and better.

Inventor’s Photo

Just as water flows into the lowlands, he tries to see the essence of things without going against the laws of nature. At the same time, he realizes that curiosity and doubts such as WHAT and WHY, which spring out in due course, are important factors for everything. Drawing starts when he thinks about the mechanism of details along this flow. Patents will be given only to things and technologies with clear stand out features. Features which seem to have been intentionally squeezed out can be detected by the authority. From that point of view, products and technologies with inventive step and novelty are to be recognized as patents.

Even after he starts drawing a target product, he will encounter various problems. At that point, he doesn’t hurry and stops the time so that he can be free from designing work and returns to his ordinary daily life. The inventor is acting in order to get hints of the task which exist in all things that we see in everyday life. Also, past experience with regard to patents could bring a great hint to him. In his case, the fact he has traveled abroad to about 40 countries, including usual traveling, business trips, and migration, would be an important factor, when it comes to inventing things and technologies.


Patents acquisition history









Mechanical multi-level parking products