This is part of Japan's tax system. If you are not a Japanese tax resident, dividends from Japanese stocks may be taxed differently, or not at all, under the rules of your own country.
How it works
In principle, tax is withheld at the time a dividend is paid (see the Withholding Tax page for details). If you receive dividends into a "with withholding" specific account, taxation is often completed without needing to file a tax return.
Choosing a taxation method
When filing a tax return, dividends may be eligible for comprehensive taxation or separate self-assessment taxation (see related pages). Dividends received within a NISA account are tax-exempt. Which method is most advantageous depends on your income situation, so please consult a qualified tax accountant.