(It is called Kashikoku-Naru-Puzzle in Japanese, which literally means "a puzzle that makes you smarter."
Miyamoto developed KenKen in 2003 to help his students improve their calculation skills, logical thinking and patience.
It was introduced to the rest of the world at the 2007 Bologna Book Fair as KenKen and has been translated into Korean, Thai, German, French, Czech, Mandarin Chinese, Simplified Chinese, Slovene, Spanish, Portuguese, and Icelandic.
He worked as an instructor at a juku (university preparatory cramming school) in Yokohama.
In 1993 he founded his own school named Miyamoto Sansuu Kyoushitsu (Miyamoto Math Classroom) in Yokohama, and established his unique "non-teaching classroom" methodology called "The Art of Teaching Without Teaching".