It depends, and it depends who's gonna buy your game.
Some things are basic Japanese fan* lingo, where other are more obscure, yes (like spreading water in the temples, as seen in Hoshimemo, it's a given and a very common custom, but I never noticed it before. I know this is not a translatable term but a custom, but it got addressed in that game properly).
After decades of repeating the same old and used tropes, it's easy to become familiar not with Japan, but with Japanese clichés.
I admit that when they reference Japanese comedians or famous people, like in some Key works such as Clannad, the best weeb can get lost.
* weeb or regular fan, what you like.