This is true, Japan's population pyramid [1] looks way more dire that Russia's [2]. Russia's does seem to suggest shrinkage after the big generation born in the 80's passes away, but oscillation afterwards. Japan's is an inverted pyramid.

[1]: https://en.wikipedia.org/wiki/Demographics_of_Japan#/media/F...

[2]: https://upload.wikimedia.org/wikipedia/commons/e/e8/Russian_...