Quarantine for domestic flights to Okinawa

Is there quarantine for domestic flights to Okinawa?
As of March 20th 2021, today...
From Osaka, Tokyo, Ishikawa specifically.
Thank you!

No, there is no and has never been any quarantine for any domestic flights.

Thank you!

Does anyone know how quarantine works for connecting-flights?
example you are japanese and need to go for a funeral of a family member from Paris to Kumamoto VIA Tokyo.

Where will be quarantine be? In Tokyo?
So the question is: Does someone need to make the stop in Tokyo before he continue to his domestic airport or can he continue and spend the quarantain then at the destination airport.

In case at the destimation airport: Also lets say the stopover time is just 1,5h.... will this be possible with all the procedures and checks within tokyo?

Did you try to ask your airline about this ? They probably know better than us. I guess many travelers are in the same situation, so they must know about it.

[example you are japanese and need to go for a funeral of a family member from Paris to Kumamoto VIA Tokyo
The airlines are not responsible for that, it is a combination of Immigration, Justice and Health. Short answer is you will basically be detained at Tokyo for quarantine for two weeks. You can easily check the current requirements at https://www.mofa.go.jp/ca/fna/page4e_001053.html
This information is and has been easily available for the best part of a year, and regularly updated.

Section 2.1 makes it clear
" Then they are required to stay 14 days at a location designated by the quarantine station chief (own residence etc.) and to refrain from using public transportation."
Further, there is a written pledge required:
From January 14, 2021 until further notice, all Japanese nationals and foreign nationals with the status of residence are also required to pledge to refrain from using public transportation for 14 days, and to be in quarantine at home or other designated areas for 14 days, retain the location data, and provide it to the health centers or other institutions, if requested. (If separate quarantine measures are to be taken, those also need to be pledged.) They are required to sign and submit the Written Pledge(PDF) when entering Japan. In case of violation, they may be subject to detention under Quarantine Act and the following shall apply:
(ú@) For Japanese nationals, names and other information that contribute to preventing the spread of infection may be made public.