Haneda is close enough to the center of Tokyo, and the Keikyu Airport Limited Express will bring you to Shinagawa in less than 20 minutes, and the express train in about 25 minutes.
This means most of downtown Tokyo (e.g. Shibuya, Shinjuku, Ginza, Ueno, Asakusa, Akihabara), as well as Yokohama, is reachable within 1 hour. So, practically, you can go anywhere in downtown Tokyo. I’d recommend somewhere with easier access, though, so maybe Ginza or Shibuya are quite appropriate.
I would suggest following any Tokyo tourist guide and pick just one or two spots to visit; but the more practical thing is probably just to do some shopping and get some Japanese food.
The only thing that you need to pay close attention is that you don’t want to miss your train back to Haneda or your flight! The last train from Shinagawa to Haneda is, fortunately, late enough though (23:58 weekdays, 23:42 weekends and holidays). But for international flights you’d like to arrive 2 hours before departure, so that leaves you maybe 3-4 hours to wander around.
This is from the official Japan site from the Ministry of Foreign Affairs:
Starting from 0:00 am (JST) on October 11, 2022, based on the New Border Measures (34), for all cross-border travelers and returnees from countries/regions where the B.1.1.529 Omicron variant becomes dominant (all countries/regions except for those where COVID-19 variants other than the Omicron variant become dominant, based on the New Border Measures (27) (February 24, 2022)), on-arrival test at the quarantine station, self-quarantine in places such as their own residence or accommodations, and refraining from use of public transportation are no longer required in principle. In addition, all returnees and entrants will now be required to provide either a valid COVID-19 vaccination certificate (3 doses) of vaccines on the Emergency Use List of World Health Organization (WHO) or a certificate of negative result of pre-departure COVID-19 test within 72 hours prior to departing from the original country/region. (NEW)
Just a small recommendation, but you can walk on the Tamagawa Sky Bridge, where you can have a decent small up view of the city and airport. Example:
From Twitter
I assume you are doing an international-to-international transit and this is happening soon, in which case I’m sorry, you will not be allowed to leave the airport. Japan remains essentially closed to all visitors and mandates quarantine even for Japanese nationals returning to the country, with some exceptions too tedious to get into and in any case not applicable for you.
As for what you can do, you will be confined to the airside facilities of Terminal 3 (fka International Terminal). Here’s a current list of what’s open when, and note that you’ll only have access to those under "after security check". It’s pretty slim pickings, especially at night, and even the paid lounges appear to close at 10pm.
Update: This answer is now comprehensively out of date. As of last week, international airports in Japan (sample size: KIX, NRT) are still quieter than usual but at least 1/3 of shops were back open. I expect that will soon rocket back to 100% with Japan reopening on the 11th, and from that day on you can also enter Japan easily even on short transits.
Credit:stackoverflow.com‘
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