Japan makes no claim to any territory on the Antarctic continent.
None of Antarctica is owned by any country. Many countries have claims, and no future claims can be made according to the Antarctic Treaty.
A small part (to the west) has Europe down South. The Other part has Asia to the South.
Europe, Japan and Canada are in the Northern Hemisphere
No. It is just like the English Channel is not part of England. It lies beneath it but it is not actually owned by them. They share a partnership with France (secretly)
Australia does not own Antarctica: it is owned by no country.
Zero.
It has 12 countries working there, but I do not know it is "owned" by any of them.
japan
The only continent that is neither a country nor owned by any countries is Antarctica. Numerous countries claim territory on Antarctica, but these claims are different from the establishment of actual "countries" on a continent. No country actually owns any part of the Antarctic, despite the territorial claims.
Japan.
Mawson is owned by Australia.
The Ozone hole is the oldest part of Antarctica
None.