I first recognized this many, many years ago when I kept getting tripped up by the local dialect, known as Hakata-ben (博多弁). I’ve written about this elsewhere, but what I’m getting at here here is not my failure to understand what someone is saying because he is speaking the local dialect, but rather people not understand what I am saying because I have unwittingly used the dialect thinking that what I said was standard Japanese.
Take the Japanese word koi (濃い), which can mean deep, heavy, dark or thick—such as in koi aka (濃い赤), “deep red”; koi sūpu (濃いスープ) “thick soup”; ~ wa ajitsuke ga koi (〜は味付けが濃い) “. . . is strongly seasoned”; or even chi-wa mizu-yorimo koi (血は水よりも濃い) “Blood is thicker than water.” For the first ten years of my life here in Japan, I thought koi was pronounced koyui. (Try looking it up in a Japanese-English dictionary.) If you go to Tõkyõ and ask a bartender to make you a stiff drink, saying “make it koyui”, he’ll probably give you a funny look.
Traditional foods, too, can vary from region to region in Japan, so much so that a simple dish like o-zōni—a soup eaten during New Year’s—can contain radically different ingredients and yet still be called o-zōni.
Customs, as I have mentioned before, also differ from prefecture to prefecture. The Bon Festival of the Dead, for example, can, depending on the region, be held as early as July 15th (around Tōkyō) or in other parts on August 15th. Some regions, such as Okinawa, observe what is known as Kyū Bon (旧盆) which falls on the 15th day of the seventh lunar month. In 2014, Kyū Bon will take place from the 8th to the 10th of August. Living all this time in Kyūshū, I used to assume that all Japanese celebrated the Bon in the middle of August and would ask everyone, “Why isn’t this a national holiday like New Year’s?”
And only yesterday it finally dawned on me that something I had taken for twenty-plus years to be a widely-observed custom was actually a very local one: sansha mairi (三社参り).
In Japan, many people (and I would venture most) visit a Shintō shrine during the first few days of the new year, a custom known as hatsumōdé (初詣), to pray or make wishes. At the shrines, they buy good luck charms called o-mamori (お守り), drink a special kind of saké, and buy written oracles known as o-mikuji (おみくじ). It’s primarily in Fukuoka, I now understand, that people visit (o-mairi, お参り) three shrines (三社) rather than one.
Live and learn.
 On one of my more recent visits to Tōkyō, a woman I was talking to said I spoke Japanese with a “charming southern accent”. Don’t know if she meant that as a compliment or not.