You will notice the additional squares at the upper and left side of each 9x9 Sudoku grid displaying all 9 reference Kanji characters. Mark the used Kanji of each line and column to avoid getting confused.
Hiragana-Kotowaza-Sudoku
Yeah, 3 Japanese words in-a-row!
See - you already started to learn some Japanese...
:-)
Learning Hiragana with Sudokus seems to be a bit odd as long as no 'supersized' Sudokus like 50x50 or so are used - yet because of the strong demand - we decided to add some value to our new Hiragana Sudokus by using Japanese proverbs (kotowaza 諺) to help you learn even more about the Japanese language & culture.
Please refer to Wikipedia for Sudoku solution methods.