Overview: The behind-the-scenes tales of hit products and creations from Japan: this is Japan's Top Inventions. This time, the worksheet study method known as "Kumon." Invented in 1958 by math teacher Kumon Toru for his son, the method involves self-study with math problems printed on worksheets. Using the sheets, learners improve their academic ability in small steps. Today the method is used by over 4 million students in 57 countries and regions. Dive into the little-known story behind this method.