Join Date: Aug 2002
Location: WAS/TYO
Programs: UA 1K, AA EXP (3MM), DL PM, BONVOY TITANIUM, HYATT GLOBALIST, HILTON DIAMOND, IHG DIAMOND AMB, et al
Posts: 6,244
No COVID test required by Japan to merely transit HND. You'll need to meet all of Australia's requirements upon check-in for your U.S.-HND flight. Also, you'll be unable to transfer between HND/NRT (doesn't sound like you'll need to, but just putting that out there).
-FlyerBeek