TOKYO -- Maki Kaji, the man known as the godfather of "sudoku" and who coined the popular number placement puzzle's name, has died aged 69.
Kaji, former president of puzzle-creating firm Nikoli Co., passed away on Aug. 10 from bile duct cancer. His funeral was attended by close relatives and held by his widow Naomi. The family is considering a separate gathering to mourn his death.
Kaji was born in 1951 in Sapporo. He competed at the National Sports Festival with his high school tennis club. After two and half years studying at Keio University, he dropped out due to the numerous class cancellations caused by the 1970 protests against the Japan-U.S. Security Treaty.
The first spark of what would become sudoku puzzles came to Kaji while he was working at a printing company, when he laid eyes on the puzzle Number Place in a U.S. magazine. Kaji established Japan's first puzzle magazine, Puzzle Tsushin Nikoli, with friends in 1980. It was in this publication that sudoku debuted under the title "Numbers (digits) must remain single" -- "suji wa dokushin ni kagiru." The abbreviated term "sudoku" became the puzzle's popular name. In 1983, Kaji founded the company Nikoli, and served as its president until stepping down at the end of July this year due to poor health.
In sudoku, single-digit numbers between 1 and 9 are placed into a nine-by-nine grid of squares. No digit can be repeated in the same row, column, or block of nine squares. Kaji took particular care over the puzzle's appearance, and crafted an original symmetrical style of arranging numbers with those already filled in by centering around the middle square.
Puzzles weren't only employees' creations, and many were constructed using ideas collected from fans. This engagement expanded the fanbase further. His company published other types of puzzle books one after another, leading to the appearance of puzzle corners in Japan's book stores.
Sudoku began gaining worldwide recognition in 2004. A New Zealander staying in London who had been hooked on sudoku during a trip to Japan pitched them to a U.K. newspaper, and sudoku puzzles began serialization. Sudoku's use of numbers, a universal concept, meant it appeared in newspapers across the world and numerous books published also. Sudoku world championships started from 2006, and Kaji was frequently invited to the competitions by organizers in different countries. "Sudoku" has an entry in the Oxford English Dictionary, and the New York Times introduced Kaji as the "godfather of sudoku."
Sudoku has also piqued the interest of scholars worldwide, with many releasing essays on it. A team of German and British researchers reported the finding that the number of possible solutions for nine-by-nine grids is 6.67 times 10 raised to the power of 21.
More difficult 16 by 16 and 25 by 25 grid puzzles, as well as easier sudoku for children and older people have also been made. Nikoli estimates there are over 200 million sudoku fans in more than 100 countries.
Kaji said in a recent interview: "I don't want to just be the godfather of sudoku. I'd like to spread the fun of puzzles until I'm known as the person who established the puzzle genre in Japan."
(Japanese original by Yasuyoshi Tanaka, Editorial Division)