He is the one who carried the family name of his wife as the tradition of Japanese when one family do not have their own male heir. Sadajiro has a father that deals in antiques. He was then sent to the Yamanaka family to have an apprenticeship. Having worked hard, he even married the eldest daughter of Yamanaka which is already known as a dealer of antique arts. Later he became the one who manages the company. He had the dream to established a branch of the business into the United States and so in 1894 a shop was opened in Chelsea in New York City.

He was just then at the age of 28. It became then a company and was named Yamanaka and Company in 1917. A 5 story building was acquired in Fifth Avenue, Manhattan. The business was a success as customers flow into the shops and they had opened more shops in different locations. People buy statues of Buddha, netsuke, tea ceremony utensils, scrolls, seal pouches, miniature figurines, bronze vases and many other. They had extended their operation into Europe and they even made donations to various places that deal with the arts.

Yamanaka then travels into the US, Japan, Europe, and Asia managing the business operations. The business is going smoothly and successful but it has the big blow into it when the war happened. The assets of the company were confiscated and sold off with nothing going for the company. After the war, an effort was made for the company to recover. It was managed by an heir when Yamanaka died but it did not last long. It had to close.