The Japanese Government's official Romanization system currently uses "tu" instead of "tsu", "si" and "zi" instead of "shi" and "ji", "syu" and "zyu" instead of "shu" and "ju", and so on. Granted, you hardly ever see a sign pointing to "Sinzyuku", but the possibility is there. And it's what they teach to English students in high schools. It's best not to use these weird spellings, in my opinion, but it's good to chronicle them so that if students encounter them, they'll know.
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The Japanese Government's official Romanization system currently uses "tu" instead of "tsu", "si" and "zi" instead of "shi" and "ji", "syu" and "zyu" instead of "shu" and "ju", and so on. Granted, you hardly ever see a sign pointing to "Sinzyuku", but the possibility is there. And it's what they teach to English students in high schools. It's best not to use these weird spellings, in my opinion, but it's good to chronicle them so that if students encounter them, they'll know.
For more, see this article in the Japan Times.