This is a set of six "Hitori de Tokkun" books from Koguma-kai. Only "Addition Basics" has been cut, but everything is included, including the answers. The others have only fold marks, and there is no writing, so I think the condition is good. I have collected books specializing in numbers and arithmetic. I think they are all good problems without any unnecessary ones. There are books for ages 4 and 5, but my child did them all at age 5. "Positional Correspondence" is also for ages 4 and up, but the latter part is quite detailed, so even a 5-year-old can enjoy it. (See image 6) On Amazon, they cost 660 yen per book, for a total of 3,960 yen, so I think it's a good deal(^^) A set of educational picture books for children, with fun illustrations. - Title: Number Composition - Title: Correspondence of One - Title: Addition Basics - Title: Number Exchange - Title: Calculations from 1 to 10 - Title: Number Guessing Game Thank you for looking. Hitori de Tokkun, Koguma-kai, 5 years old, 4 years old, 6 books, numbers, arithmetic, position