overlay in japan

Hi. i'm a Vietnamese passport holder and i also have US green card. i have a flight from vietnam to San diego and will overlay in Narita Airport for 11hrs. i want to know if i can go out for a quick sightseeing and enjoy some food in Tokyo . Is there any visa or requirement needed . thanks

You should research this yourself by going to the website of the Japanese embassy in your country.

if Vietnamese people need a visa for japan, then you probably need it, even for short time.
i dont think there is the possibility to "just browsing..." into a country for a few hours. if you leave the transportation hub at customs and exit to japan, then you also probably need the visa and do all the formalities.

please take care that those can take 2h and you probably need again 2h to enter back. but well, it should be enough time to check for example this: https://www.japan-guide.com/ad/naritasan/

Thanks for your advice. I just concern that some people told me that if i have the US green card. They can approved at the customs without visa

yes, this could be.
sorry i dont know about that, please try to ask your embassy