China gets land access to a port along the coast of the sea of Japan, east of North Korea, in land today controlled by Russia

It could be via conquest or negotiation or other methods. As long as they can carry things into it directly from the rest of mainland china to load onto ships.

Doing it through north Korean land doesn't count.they must control the port for at least a month and it must be really working and loading shops. Not just plans or construction.

Note: when talking about land, I'm referring to 2023 ownership. So even if China officially buys NK land and then builds a port, it won't count, since that's still 2023 NK land. They have to do it through 2023 Russian land.