© ReutersRussian warships in a 2020 Navy Day parade.
"It is absolutely obvious that it is impossible to discuss the signing of such a document [a peace treaty] with a state that takes openly unfriendly positions and allows itself direct threats against our country," the official said.
The two countries have long been locked in a standoff regarding competing territorial claims over islands off northern Japan, disputed since the end of WWII, but which have come under increasing militarization by Russia.
For example, Russian forces have just in the last month deployed new missile defense systems in the disputed Kuril Islands, as part of what looks to be a semi-permanent forward positioning of troops, specifically a mobile coastal defense missiles system on a northernmost island in the chain, Paramushir.
Russia knows the island chain as the Kurils while Japan calls them the Northern Territories. Russia has long been denounced by Japan and its allies in the West for sending military assets there.
The Soviet Union had annexed the islands during the final days of WWII, and the status of ownership of the islands, which Russia de facto currently controls, is still unresolved and as a treaty regarding their status has been subject of on-again, off-again negotiations with President Putin.
As for the fresh Kremlin statement on Japan's "unfriendly positions" which make negotiations "impossible" - this appears a reference to Japan joining the Western initiative to impose sweeping sanctions on Russia over its invasion of Ukraine.
Japan surrendered UNCONDITIONALLY to the Allies in 1945 and that, by definition, means that they have no say about any terms that are imposed on them. Just because the process of a formal treaty with the SU (and subsequently Russia) has been stretched out for nearly eighty years does not mean that they can now rescind their unconditional surrender.
Since no formal peace treaty following the unconditional surrender was signed, all of the territorial losses to the SU (and now Russia) are completely valid and legal under international law. Calling the territorial disagreements "unresolved" is nonsense - they are fully resolved, i.e., they are unequivocally under Russia's jurisdiction, period.
Of course, Japan is free to complain all they want, but especially given that Japan is currently a de facto hostile country towards Russia, Russia has literally zero obligation to even discuss or consider any of Japan's demands, requests, etc.