Japan famous for their outgoing and expressive culture

Nah man, there would be some form of cultural disdain for types of tails. It would become another form of racism. Got your culture, looks, skin color, etc and at the end "tail type". There would be whole sociocultural wars started over tail length. People would go around hiding their tails claiming fashion forward practices to fit in.

Politicians would claim bus seats with holes aren't safe in order to put down the people who primarily use them. Activist groups would come out saying that pants with openings for tail comfort goes against the teachings of the Great Tailed God. Eventually there would be a change towards equality, though never justice. Beneath the false peace people would still be whispering and somehow those few with the "nicest" tails, born into fabulously-tailed families, would always have more privilege and often not understand how having a different tail can be an automatic disadvantage.

There is probably a good reason we don't - it evolved out because we seem to be benefited by hiding our emotions

Though the causal link might be the other way around - if we were better with dealing with expressed emotion we could have kept the tail

Could probably look at the taxonomy to see when we lost it and what happened to our tailed brethren