As astonishing as its vigor is the fact that Russia's eastward expansion, beginning in the 16th century, went all but unnoticed, by Japan no less than by Europe.
Japan and Russia were bound to meet. Russian sailors reached the Sea of Okhotsk in 1639. By 1715, Russian traders were in the Kurile Islands and in Sakhalin, on Japan's very doorstep. Japan at the time was shuttered against the outside world — no one allowed in, no one allowed out; official policy since 1638. Japan's rulers knew two damning facts about Europeans: they were Christians and they were colonizers. Thus sakoku, the defensive "closed country" policy.
There was intermittent contact nonetheless. Russian and Japanese traders and trappers mingled in the northern islands. At intervals a Russian ship would approach Japan, seeking trade. The Japanese replied that their law did not permit dealing with foreigners except under very tight restrictions at Nagasaki. The Russians could try their luck there if they liked; otherwise they'd better make themselves scarce. Russia did not press the point. It hardly seemed worthwhile.