Japan and Sakhalin – Wikileaks
Japan has been involved in a territorial dispute with Russia since the end of World War II over islands to the north of Hokkaido, including and very close to Sakhalin.
Despite the Kuril Islands dispute, That hasn’t stopped Tokyo is still doing business with Sakhalin, according to one cable:
In a recent meeting with Embassy officials in Sakhalin, Shell oil representatives stated that no LNG (liquified natural gas) had been shipped from the Sakhalin II facility to the U.S. due to soft prices in that market. Much of this LNG has been shipped to Japan instead.
Business is business, after all.

The territorial dispute has never extended to Sakhalin, except in the minds of some of the craziest “restore the emperor” righties.
EDIT: Meaning the postwar dispute, of course. Japan wants the smaller islands closer to the Hokkaido coast returned, but I’ve never heard of any postwar demands for the return of the big one.
Thanks for this Durf. I’ll go in and do an edit now.