[sgxin]

Another strategic moves and counter moves by the superpowers and allied regional powers to out manoeuvre each other.

This move allows naval projection by adversarial nuclear submarines off Japanese shores which is a stone throw away.

I think it is quite unlikely for the Vladivostok port to support Chinese naval vessels as it would require Russia to allow China to setup a military support base there for naval ship repairs and replenishment.

A more viable scheme for a China naval base in the Sea of Japan will be via NK. Unlike Russia, NK is indebted to China for the latter's help during the Korean war.
China could lease the short 15km land strip along 图们江 on the NK side that separates Jilin 珲春 city from the Sea of Japan.