Japanese people tend to see their society as homogeneous, and it is in many respects. But there is a noticeable cultural live between Western Japan and Eastern Japan.
The way people speak is different (e.g. なんだ in Eastern Japan vs なんじゃ in Western Japan; stressed syllables on homophonic words like hashi or kumo are the opposite).
Food is different. For example in Eastern Japan white miso is more popular while in Western Japan red miso dominates.
Eastern Japan uses 50 Hz TVs against 60 Hz for Western Japan.
People in Western Japan tend to be more outspoken and outgoing while those in Easter Japan are more reserved.
I'm sure that there are other differences too.
Interestingly this cultural divide seems to follow exactly the tectonic divide that splits Japan around the Chūbu region between the Eurasian plate and the North American plate.
There is also an East-West difference for vegetables, although a bit less clear cut. Western Japanese are more likely to eat Chinese cabbage, while Easterners consume more radishes (daikon), bean sprouts (moyashi), wakame and leafy vegetables.
Silly question, but wouldn't the food-related differences correlate to climate rather than tectonic plates?
And while legend has it that people from Osaka are more outspoken and assertive, I am unsure whether the same can be said about the rest of Western Japan (Kyushu, Chugoku, or even the other regions of Kansai).
I never said that the tectonic plates were the cause of the east-west cultural divide. It just happens to coincide with it.
The local availability may play a role for fresh products like seafood (shellfish, crabs, shrimps), which is why I did not list them. But I don't see how climate or the local environment can influence the type of meat consumption.
Here is another interesting east-west divide: nattō consumption. This has more to do with personal preference (whether one likes it or not) than local availability.