[Sombre]

I thought it might be interesting to have a late period Japan where they've been heavily influenced or semi-conquered by LA Marignon forces, representing contact between the Portuguese / Spanish and Japan. Of course in history this was a gunpowder and cannon period, but it would still provide interesting inspiration for some sort of LA Jomon.

You could also have a MA / LA Jomon supposing they had been conquered by the Khans and their barbarian hordes, since historically the Mongols came close to launching a serious attempt on parts of Japan (stopped by bad / divine weather and distracted by other concerns).

Would your classical era Japan be EA?