Maki Kaji, a university dropout who turned a numbers game into one of the world’s most popular logic puzzles and became known as the “Godfather of Sudoku,” died at his home in Tokyo on Aug. 10. He was 69.
His death was announced on Tuesday by the puzzle company he co-founded, Nikoli. The cause was bile duct cancer, the company said in a statement.
In a speech in 2008, Mr. Kaji said he first “fell in love” with a game called Number Place in 1984. He renamed it Sudoku.
“I wanted to create a Japanese name,” Mr. Kaji said. “I created the name in about 25 seconds.” The reason: He had been in a rush to get to a horse race. He said he had not expected the name to stick. (“Sudoku” roughly translates to “single numbers.”)
By then, with two childhood friends, he had started the company that would later become Nikoli, which, according to the company, is among the most prolific global publishers of puzzle magazines and books. The company helped catapult Sudoku into the mainstream in the mid-2000s. It was Japan’s first puzzle magazine, the company said in its statement.
The company itself does not create many new puzzles — for example, an American is believed to have invented an earlier version of Sudoku. But the true origins are murky. Some trace the game back to Leonhard Euler, an 18th-century Swiss mathematician. Others say the idea came from China, through India, to the Arab world in the eighth or ninth century.
However the puzzle was created, Mr. Kaji’s company made Sudoku and other similar puzzles popular globally. Nikoli’s secret, he told The New York Times in 2007, was that it largely tested and perfected existing puzzles.
“I want to make Nikoli into the world’s source for puzzle games,” he said. “We have a lot more puzzles where Sudoku came from.”
In the late 1990s, when he pitched the Sudoku puzzle to publishers in New York and London, he was unsuccessful, he told The Times. But within a decade, the puzzle was being published across hundreds of newspapers globally, generating millions of dollars.
According to Nikoli, an estimated 200 million people in 100 countries have solved the logic puzzle, which involves filling in a numbered grid. A world championship is held each year.
In 2017, an older man living in temporary housing in Otsuchi, a town in northern Japan, after the devastating 2011 earthquake, wrote Mr. Kaji to inform him that his puzzles were too difficult, the company added. That inspired Mr. Kaji to create more accessible puzzles for children and older people.
Mr. Kaji was born on Oct. 8, 1951, in Sapporo, Japan, to a father who was an engineer at a telecom company and a mother who worked at a kimono shop, according to a book he wrote on the Sudoku world craze. He graduated from Shakujii High School in Tokyo, but dropped out of Keio University.
He is survived by his wife, Naomi, and two daughters.
Puzzle experts described Mr. Kaji as having imbued their world with “soul.”
“His most important contribution to the world of logic puzzles is subtle and underappreciated,” Nick Baxter, the captain of the U.S. Puzzle Team, which competes in the World Sudoku Championship, wrote in an email.
In an age where most Sudoku and similar puzzles are computer generated, Mr. Baxter added, Nikoli continued to make puzzles generated by humans.
In an interview with the BBC in 2007, Mr. Kaji said that the secret to inventing a good puzzle was to make the rules “simple and easy for everyone, including beginners.”
He stepped down as head of his company in July because of ill health.
Despite the millions pulled in by the Sudoku puzzle, Mr. Kaji said in the interview with the Times that he had received only a small fraction of the money, in part because he had been late to trademarking the puzzle.
But he had no regrets, he added.
“We’re prolific because we do it for the love of games, not for the money,” Mr. Kaji said.