Taxes over 183 days if not earning income

I am a USA passport holder and might stay over 183 days in Japan this year on tourist visa waivers. During all this time I have not been working, only living on savings (occasionally getting some money sent to me from an old friend who is paying me back, but that's all).

What are the tax implications if I stayed, say, 200 days in Japan over the past 365 days, but was not earning any real income during this time? I am below the threshold of paying US taxes, so would not be required to file a tax return with the US.

And to make sure, it is 183 days over a rolling 365 day period, not a calendar year, correct?

Thank you lots for any info! :)

What are the tax implications if I stayed, say, 200 days in Japan over the past 365 days, but was not earning any real income during this time? I am below the threshold of paying US taxes, so would not be required to file a tax return with the US.
You would be tax resident in Japan. I do not think you would have obligations for resident taxes. (Residents earning zero do have taxes to pay.) Tour US filing obligations are not relevant. Your income is the relevant issue.

And to make sure, it is 183 days over a rolling 365 day period, not a calendar year, correct?
Correct, 183 days out of any 365 days for taxes. That is what I have observed is the international benchmark and it applies in Japan. you can certainly stay much more than that an not have an issue with immigration if your visits are genuine and under the visa waiver programme.

Thank you for the info. To clarify, I would be a tax resident AND would need to file my taxes with Japan, although the amount I would owe Japan tax authorities would be at or near zero due to me not earning an income during that time period. Is that correct?

At this stage would would probably be better to consult a tax expert (accountant or lawyer) with specific knowledge because every situation is different. Some firms offer a free initial consultation where you can get most of the information you would need without actually paying.
(As a footnote to "free" consultations, it also helps if the "expert" actually knows what they are talking about. One expert company (legal) I consulted gave me woefully incorrect information which was corrected by a second opinion that I sought. The second company I have been using for almost a decade.)