Searching AMS - TYO on Google Flights on my phone - UK based, China Eastern via Shanghai comes in at around £550 for various dates in November and start of December, travelling midweek.
China Southern can be had for £426 on same dates via Beijing but with long overnight layovers in Beijing each way.
Prices January to March are between £550 and £800.
I found it was cheaper to select KIX rather than TYO.