Aug. 17 (UPI) -- Maki Kaji, a Japanese businessman who became known as the "Godfather of Sudoku" after helping to popularize the numbers game almost two decades ago, has died of bile duct cancer. He was 69.
His puzzles company, Nikoli, said in an announcement on Tuesday that Kaji died a week ago.
"The cause of death was bile duct cancer. He was 69 years old."
Kaji was born in 1951 in the northern Japanese city of Sapporo. He later dropped out of college and founded Nikoli with a friend. He retired as Nikoli CEO on July 31 but remained a board member.
The precise origins of Sudoku are unknown, but some say it dates back to the 8th or 9th century. U.S. architect Howard Garns is often credited as the modern creator of the puzzle, which he named Number Place.
Kaji took inspiration from Garns' game and created modern Sudoku, a gridded numbers puzzle that remains popular around the world today.
Kaji said he wanted to create a Japanese name for the game and settled on Sudoku -- "su" standing for numbers and "doku" meaning single.
"In 1984, I first met Number Place. It was a very interesting puzzle, fun to solve," Kaji said in 2008. "At that time, I had already founded Nikoli and started publishing the first puzzle magazine in Japan. I fell in love with Number Place and decided to have it included in our menu.
"Since then, our team has produced thousands of Sudoku puzzles, from easy ones to difficult ones, while adding a high-quality Nikoli taste."
Sudoku is now played around the world in traditional written form and in digital form.
Kaji is survived by his wife and two daughters.