Most people will have never heard of Mr Maki Kaji, but if you are one of the millions around the world addicted to the number logic game Sudoku, you owe him a small debt of gratitude.
In 1984, he found a variant of the game in an American puzzle compendium, sans the name it is now best known by. The mind-stumper had existed for more than a century in Europe and the United States, in different forms.
Mr Kaji, now 62, tested it on the readers of his own puzzle quarterly Nikoli and after some polishing, he launched it in his home country of Japan. After a time, he give it its now famous name, a contraction of the Japanese phrase for "the digits must be single".
Mr Wayne Gould, a New Zealand-born judge based in Hong Kong, discovered the brain-teaser in a Japanese bookshop and sold the concept to The Times newspaper in London in 1997. It sparked a craze in Europe and then around the world, helped in part by the unifying brand name created by Mr Kaji.
Now in Singapore as part of a tour to promote the game in schools and other associations, the Godfather of Sudoku, as his promotional material states, tells Life! about how his role today as president of Nikoli is being an ambassador for the puzzle, which he hopes to promote to newspapers and magazines as reader entertainment.
His Tokyo-based publishing house has 23 members of staff, largely in editorial, and mostly involved in puzzle creation, either crafting new editions or testing ones submitted by readers. The company is also a supplier of Sudoku puzzles to newspapers, 150 in Japan and 18 around the world.
In Japanese and halting English, he explains why Nikoli retains human puzzle crafters, whose names are printed next to the grid squares.
While it is easy and cheap to create computer software that generates valid Sudoku games, machine-made grids tend to be chaotic, lacking the symmetry of structure that fans find so satisfying.
"Each puzzle is like a movie and the puzzle-maker is a movie director. They put a story inside it. They each have their own character, embedded in the game. Each puzzle-maker has fans. That's why we print their names next to each," he says.
Nikoli has published smartphone apps for Sudoku and other games, but the paper format will never die, he says. His company still sells 20,000 copies of its main puzzle book each quarter. He takes a page from a Nikoli book and unfolds it, revealing a much larger puzzle sheet.
"How do you view this kind of page on a smartphone screen?" he asks.
He is philosophical about what it means to have helped give birth to the current-day boom in Sudoku. He has never sought to trademark the name, he says. He might have become a very rich man, he says, laughing - "I'll just spend it in Las Vegas" - but a likely outcome might have been that newspapers would simply run the puzzle with another name and he would have missed his claim to fame.
"If I had copyrighted it, I would not be here talking to you or to all the people I have met on my trips around the world," he says.
The game's universal appeal lies in its simplicity and its graded challenge levels, says the father of two daughters, aged 28 and 36. It uses universally recognised Arabic numerals and logical thought, rather than skill in calculation, he says.
The godfather of the game considers himself a below-par Sudoku solver, having seen how experts do it at competitions and meet-ups around the world. "In Kuala Lumpur at a national competition, I saw a kid solve one in four minutes. I was shocked," he says.
The frequent world traveller prefers "a smoke and a drink" while waiting for flights, rather than sweat over a puzzle, like so many travellers and commuters do.
His advice for the many who have tried and failed at Sudoku: Don't get worked up over it and think that there is something wrong with you. It is a common problem, he says.
"Go away and do something else, and come back to it later, if you want. It's okay," he says.