The philosophy with which he lived his life — and made his puzzles — inspired him to rework an American puzzle into what would become Sudoku, one of the best-known and most widely played puzzles in the world.
And Kaji, who called himself the “Godfather of Sudoku,” was a once-in-a-lifetime creator.
The publisher and puzzleman, whose Sudoku quietly entertained players in his native Japan and across the world, died this month from bile duct cancer, according to Nikoli, the puzzle magazine company he founded. He was 69.
He handcrafted Sudoku puzzles
He developed a number of puzzles with Nikoli, but his dalliance with Sudoku began in 1984. That year, Kaji came across a puzzle in an American magazine called “Number Place.” Kaji enjoyed solving the puzzle, but he had some notes.
So, before unveiling his own version of the puzzle to appear in an upcoming Nikoli magazine, he revised its design and renamed the puzzle Sudoku, which is a shortened version of a Japanese phrase that in English means “the number must remain single.”
Sudoku’s appeal was its simplicity: Only the numbers 1 through 9 were used, none of the numbers could be repeated in a row of the nine-by-nine square and no math was required. All it took was filing them in, completing the puzzle and erasing them again so the puzzle could be passed onto a new player.
Sudoku went global, but Kaji resisted international fame
It took many years for Sudoku to become a hit in the rest of the world, but in the late-1990s, the puzzle started appearing in Western newspapers. By the mid-2000s, magazines in the UK, US and other pockets of the Western world were publishing their own Sudoku puzzles. But Kaji had only trademarked Sudoku in Japan — the rest of the Sudoku puzzles were copycats he didn’t have a hand in.
But that was all right with Kaji. In his 2008 speech, he said he thought, “‘I would be happier to see everyone in the world enjoy Sudoku more easily.'” His hand-drawn style would have slowed down production time, after all, and Sudoku’s ravenous international players could hardly wait for a new puzzle.
“They’re just for fun, for no reason, with no goal in mind,” he said.
The worldwide Sudoku boom delighted Kaji, but by that point, he’d already found contentment.
“I did not become a millionaire, but I’m glad Sudoku is now loved by billions of people,” he said at the 2008 championship. “I enjoy my staff saying they are proud of their job, I enjoy a glass of wine with my wife every night, and I enjoy horse racing every weekend. I am very much satisfied with the way I am.”