Takeo Sakata was contracted by a leading international seed company to grow seeds and he continued to actively participate in the breeding selection process to improve cultivars – including South American petunias – while still growing seeds and selling them to the Japanese market. In response to a request from Dr. Hiroshi Terao of the National Agricultural Experiment Station, he also imported double flower petunias from overseas companies.

These petunias were used by a researcher named Woo Jangchun, who discovered that double flower petunias were genetically dominant to single flower varieties. Confident that success would be guaranteed if a petunia could be developed that would yield only double flowers, Takeo devoted himself to all-double flower petunia breeding and seed production.

After several years of trials, not only had Sakata achieved outstanding success by developing F₁ petunia seeds that yielded only double flowers, but also 80% of the blooms featured beautiful, wave-like petals, resembling the designs on the handball used in the traditional Japanese game "Temari". The other 20% were carnation-type blooms. Within a few short years, people were commending this "Sakata magic" and orders for this all-double flower petunia were flooding in from seed companies worldwide.

As there was a monopoly on the product, it was traded at high prices. According to the Chicago Herald Examiner (June 20, 1935), Sakata's all-double flower petunia seeds were sold at $10,565 per pound (454 g), about 20 times the value of their weight in gold, which speaks volumes about how greatly these tiny seeds – which are smaller than poppy seeds – were valued.

In 1934, the All Double Petunia "Victorious Mix" won silver medal at the prestigious All America Selections (AAS), and from then up until the start of the Pacific War in 1941, new varieties of petunias from Sakata would go on to win eight silver or bronze medals.

After the Manchurian Incident in 1931, immigrants from Japan began to arrive in China in large numbers. Exports from Japan of vegetables, grains, and pasture grass seeds significantly increased with the development of this new market. In 1936, Sakata Shokai established the "Ofuna Farm" to focus mainly on vegetable breeding techniques. However, the second Sino-Japanese War broke out and seed exports began to come under pressure from the government.

Throughout these trying times, Sakata Shokai remained committed to its original mission of developing unique and high-quality products. The result of this perseverance was the world's first F₁ cabbage, "Suteki Kanran".

In line with the nationalist policies introduced in January 1942, which encouraged the merging of seed companies, in December Sakata Shokai was dissolved and merged with four other seed companies to form Sakata Seed Corporation, with Takeo appointed as the President.

On May 29, 1945, a major fire broke out as a result of the Great Yokohama Air Raid, and the company buildings were destroyed. Takeo, who was 56 years of age at the time, resigned and left everything in the hands of Imasuke Aso, while Sakata and his family evacuated to their cottage on Lake Yamanaka.

On August 15, 1945, the war ended with Japan's defeat. Sakata Seed Corporation, which once employed 170 people, had only 20 working for them at the time. The company's misfortunes continued after the end of the war as "Ofuna Farm" was expropriated as part of post-war government reforms.

Imasuke Aso, the new president, managed to guide the company through the post-war chaos but in the early summer of 1947, he visited Takeo and asked him to return. After a few hours of heated discussion, Takeo yielded to Aso's request and once more became president. He was 58 years of age at the time.