Purple sweet potatoes were developed to help Shochu become more widely loved.

From the perspective of sweet potato variety development,
We get closer to the birth of Aka Kirishima.

"Aka Kirishima is truly amazing. I wondered if it was really Shochu. I was convinced that this would work," said Dr. Osamu Yamakawa, a leading expert in Aka Kirishima Research who developed Murasaki Masari, the sweet potato used to make Akakirishima, unable to contain his excitement as he recalled the shock he felt at the time.

Dr. Yamakawa's encounter with Kirishima Shuzo dates back to around 1972. Dr. Yamakawa was conducting Research on sweet potatoes in Miyakonojo City, Miyazaki Prefecture, when he first tried Kirishima Shuzo 's Shochu. It had a taste without any potato smell, and was refreshing to drink. He was surprised and impressed by the new possibilities of Shochu.
At the time, there was a meeting held once a year in Miyakonojo City where Shochu companies would share information, and Dr. Yamakawa attended the meeting with the role of promoting the joint use of sweet potatoes with private companies. Kirishima Shuzo Shuzo was also in attendance. As the exchange of opinions became more lively, Dr. Yamakawa made up his mind and said, "It's no good if we just make Shochu using Koganesengan. We need to use a wider variety of varieties to make Shochu that will be accepted outside of Kyushu." The room instantly fell silent. The atmosphere was one of "Research who don't know anything about Shochu making are saying unnecessary things."
However, this was the "frank" opinion of Dr. Yamakawa, who has built a career as a sweet potato Research outside Shochu culture.
The "Kogane Senkan" variety, registered in 1966, has been highly valued in Shochu production in southern Kyushu, but considering the future of Shochu, it would be good to turn our attention to other varieties. We should create unprecedented flavors and develop them in areas outside Kyushu where Shochu is not accustomed to drinking. That's what Dr. Yamakawa thought.

Time passed, and around 1991, Dr. Yamakawa was tasked by the government with restoring demand for sweet potato cultivation. His proposal was to develop sweet potatoes with flesh colors such as purple and orange, which could be used as a pigment, unlike the mainstream sweet potatoes that had been used up until then.
"I'm not the type of person who is too picky about things. No matter how traditional something may be, if I don't think there's much hope for the future, I'll quit. I'm only interested in new things."
This challenge represented a major change in Kyushu, where the development of sweet potatoes for starch had long been the norm. However, the time available was short.

"Normally, breeding takes about 10 years, but they said they couldn't wait that long and wanted it done in three to five years. I felt that I had to take responsibility and push forward with it or we wouldn't make it in time."
All they could do was breed them relentlessly. They resolved to immerse themselves in the mind-numbing task and continued the repetitive work day after day.
And finally, it appeared. Ayamurasaki, a highly fragrant variety with a vibrant purple color derived from anthocyanin pigments. Amazingly, Ayamurasaki was the result of crossbreeding with a variety that lacks pigments. Dedicated crossbreeding was a success.

Ayamurasaki was developed as a dye, but demand for it at the time was minimal. There was little hope of it becoming popular in the market. The only option was to change perspective.
Dr. Yamakawa teamed up with Kirishima Shuzo, which was keen to try making Shochu using the new variety, and began test production of the new variety as a Shochu ingredient. While Ayamurasaki was excellent for coloring, it was not suitable as a Shochu ingredient. It had a bitter taste and an iron-like aroma. Its shape was also uneven, making it difficult to handle. But that didn't mean he could stop.
Dr. Yamakawa patiently continued to improve the varieties until he found one suitable for Shochu production. He tried and tested again and again, conducting brewing tests every time a new variety was released. After many failures, "Shiyu" was born. As a Shochu ingredient, it far surpassed Ayamurasaki.

The development team at Kirishima Shuzo spent six years working tenaciously to commercialize Aka Kirishima, and it was finally completed. Dr. Yamakawa was given a taste of it shortly after it was completed.
Even Dr. Yamakawa, who doesn't normally drink alcohol, was impressed by the delicious aroma, sweetness, and soft taste.
Aka Kirishima has now become a product loved by a wide range of customers for its flavor, which is exactly what Dr. Yamakawa said we should aim for at that meeting.

"Shiyu" is the fruit of Dr. Yamakawa's long and arduous Research. When asked why he decided to entrust such an important variety to Kirishima Shuzo, he replied:
"In the end, it all comes down to honesty. The employees at Kirishima Shuzo were the only ones who persistently continued to consult with me. They always gave me feedback on the varieties I entrusted to them, so I knew I could trust these people."
The nostalgic look on his face as he spoke conveyed the trust that the two had built up.

"There are no treasures on the path that people have walked," says Dr. Yamakawa. It was probably Dr. Yamakawa's determination to look into the future where no one has ever walked before that brought the treasure that is Aka Kirishima to Kirishima Shuzo.