While Japan has a long and rich history of printing, the earliest known printed books date back to the 770s AD, using the woodblock printing technique.
The Diamond Sutra, printed in 868 AD, is the oldest known example of a printed book from China.
It's important to differentiate between the date of the book and the date of printing. Some manuscripts predate 868 AD, and they may have been copied and reprinted throughout history.
If you are interested in learning more about the history of printing in Japan, I recommend you research the Diamond Sutra, as well as the early history of woodblock printing in Japan.