Taxes

Japan has an 8% sales tax.
So everything you buy here, you pay 8% more for taxes. But you don't need to leave any tips in restaurants or services, so that is nice.

If you are a tourist, you don't need to worry about any other taxes.

And its nice that if you bring your passport, mnay stors can sell you their producs without charging the taxes. So if you plan to buy any expensive electronics or other goods, you can save 8% on their price. Big stores that I know have tax free are: Yodobashi Camera, Bic Camera, Donkijote. But many smaller shops have tax free as well, just look for this logo:
https://cdn.cheapoguides.com/wp-content/uploads/sites/2/2016/08/Tax-Free-Shopping.jpg

If your question is about living in Japan, then that is a whole other conversation, let me know if that's hat you need to know instead. :-)