Here is the form, with antigen listed.
https://www.mofa.go.jp/files/100177968.pdf

I am no chemist, but it seems chemiluminescence is okay, and immunochromatographic is out.

In terms of antigen, do note that the form distinguishes between qualitative and quantitative antigen tests. I can't say I know what the difference is, but make sure that it is the right kind you go for.
​​​​​​

From what I could figure out, chemiluminescence is quantitative (CLEIA), and immunochromatographic (ICA) is qualitative. Problem is US doesn't seem to use that terminology.

This was the same form I used on Monday. :p

I know the BinaxNow test is the most popular antigen test in the US right now, but appears to be “qualitative”. If anyone knows of a cheap “quantitative” test, please share!

“The BinaxNOWTM COVID-19 Ag Card is a lateral flow immunoassay intended for the qualitative detection of nucleocapsid protein antigen from SARS-CoV-2 in direct anterior nasal (nares) swabs from individuals suspected of COVID-19 by their healthcare provider within the first seven days of symptom onset.”

Is there a reason why you care about the difference?

Qualitative = yes or no.

Quantitative = a number, but almost every lab provider warns you about the lack of research about this number, and you can't compare it to a different lab's number.
and most likely this will be a molecular test. There are two takehome molecular tests using LAMP, both claiming to be the first FDA EUA athome molecular tests (Cue and Lucir) but i believe they only report yes/no
​​​​​

Speculating if a quantitative antigen test, was the free and rapid test mentioned earlier that would qualify for entry into Japan. Unless there’s a different test you’re aware of that satisfies entry into Japan that is free and within 30 minutes. I’ve been looking for one without much success.

I wish I had more details. This summer we met some Japanese who entered after getting free test in the US, but I have no way of verifying exactly which tests they were. My son knows Japanese in NYC who have done so as well, but again, no details have been passed on to me.

I'm flying ICN-NRT on OZ and NRT-ORD on ANA on separate tickets. Can OZ still check my bag through to ORD? I called Asiana to confirm and they said "maybe, but you should ask the check-in desk on the day of your flight."

That's really a question for the OZ forum, and what their policies are and general experices. Some airlines do, some airlines don't. Narita and ANA has no rules blocking it from happening.

That advice isn't very reassuring unless you travel very light.
A somewhat similar question came up on a UA award on OZ, JFK-ICN, 16 hour layover, ICN-KIX. At first the Japan-based UA agent wasn't sure the bags would be checked through, but after talking to OZ they called me back and said no problem. I called OZ and they confirmed it. If I were you I would talk to another OZ agent and ANA as well.

Transit at Haneda or Narita covid
 

Can we transit at Haneda even though Japan is closed for tourists?

I googled your query. From the US Embassy in Japan website, "Travelers seeking to transit Japan en route to onward international destinations may continue to do so without quarantine as long as the transit occurs within the same airport and no overnight stay is required."

The above information is also confirmed on a number of other websites, including the UK govt, ANA, JAL and Philippine Airlines.

Do ANA and JAL have a baggage interlining agreement between international flights at Haneda? Back in 2019 I was able to take advantage of the agreement at Narita for a 95 minute connection to Taipei, but I’m unclear on whether that was unique to that airport.

They certainly have an interline agreement, all of the big carriers do. The question really is, will they check luggage in across two separate tickets, which is a separate point after having the interline agreement.

Generally, both of them are quite good at checking luggage through to other carriers on separate tickets, JAL has it as stated policy to any Oneworld carrier. I don't believe either has a policy that includes non-alliance carriers, so to some extent it will be up to the check-in agent of the day. But generally I would say yes they do.

If we are talking a single ticket, that's no issue at all. Luggage will be passed between the two carriers.

Oh, wow! I was under the (mistaken?) impression that for Narita at least, checking through from ANA to JAL was an official thing. On that occasion it was two separate award tickets (ANA award + BA award). I wouldn’t have risked it had I known otherwise.