No, transits are not banned in Japan. restrictions are on entry to the country. Meaning transit will need to be in the same airport, you can't go between NRT and HND, and it can't be overnight in Narita as the terminals closes for the night.

I would fly a friend up from Kansai, have them rent a car, pick her up, return the car and then fly together with her back to Kansai from Haneda. Not an issue for Japanese nationals.

Overnite Layover Narita
 

Looking at a booking HKG-TUL with two stops, NRT + DFW. The stop at Narita is from 4PM to 10AM. It seems to me the only option is to stay within the terminal on the secure side for the duration. Foreign nationals from Hong Kong cannot currently enter Japan. The capsule hotel in the airport is closed.

Am I missing anything?

Is the secure side open 24h?

NRT is not 24 hrs. airport. Passengers cannot stay overnight at secure side of the terminal. HND is the one with 24 hrs. operation where passengers can overnight at secure side of the terminal.

Connecting in NRT
 

Has anyone connected in NRT since the covid19 restrictions went into effect. I am flying UA GUM-NRT-EWR, and have been in the mainland USA in the past 14 days. UA said it should be no issue, I just can't leave the transit area due to the covid19 entry restrictions. Any one know of any new screening measures on arrival in NRT? I am assuming just a temperature check.

I can't find any website that can positively confirm transits (from countries not allowed to enter Japan) are allowed through NRT at all. I'm a US national living in HK and am looking to fly HKG->NRT->SEA round trip in early August, but I'm not sure if this will be allowed or if there's quarantine implications.

According to American Airlines today, June 23, same day transits through NRT are not an issue (i.e. not transiting out of NRT to another airport).

I am trying to book award ticket using AAdvantage from Taipei to Chicago in early August. I am trying to make one connection. The only option to fit this criterion is to fly

TSA (Songshan Airport) - HND 14:20 - 18:30
HND - ORD 11:45 - 09:45

So this involves an overnight connection at HND airport. Due to the current restriction, I cannot enter through immigration, so I have to stay in the airside for that length. I don't mind doing that, but is it currently possible to do this? I know HND international terminal airside normally opens 24 hours, so that should be possible in normal situation. But is it still 24 hours during the pandemic period?

It is. The airside part of the transit hotel was closed until the 30th of June, at least. I have not checked if the did actually reopen July 1st. With the lack of traffic development, I would guess no. But there is always a bench, or the floor.

The transit hotel website appears to show no availability through Aug. Might be worth calling to verify.

Once my typo was corrected, that would kind of be my expectation.

Thanks for replies. At this time as long as I can get back, I cannot ask too much. So it is fine that transit hotel remain closed. I am okay to just hang around transit area overnight even though it is going to be really long hours to kill.

I also saw an option of NRT overnight connection. But then I realized I had to enter immigration because NRT closed at night. So the option was out because of entry restriction right now.

Is Japan allowing transit now (new guidelines came out July 1st)? I'm considering flying from Singapore to the US via NRT (on JAL), but it's not clear whether the ban of people who're coming from Singapore applies also to transit.

The notice on the JAL website (I'm not allowed to post a link here) says the ban applies to "landing" and not just "entering"?

Transit is allowed. But please note that you can't change airport between Haneda and Narita or vice versa as that would require you to enter Japan. You can't have an overnight connection in Narita, but you can in Haneda.