The Hepburn romanization, to express the different realizations of some consonants before /i/ or /u/, uses different spellings from the other syllables in their groups:
- /si/ > "shi"
- /zi/ > "ji"
- /ti/ > "chi", /tu/ > "tsu"
- /hu/ > "fu"
Other romanizations, like the Nihon-shiki or Kunrei-shiki, avoid this altogether sticking to one consonant symbol for each group.
Have there ever been any romanization standards which instead used diacritics to express this difference in pronunciation? E.g. something like:
sa ši su se so za ži zu ze zo ta ťi ţu te to ha he ḩu he ho