Romanizations of Japanese using consonant diacritics?

Question

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

Answer 1

No romanization systems currently in use today use diacritics on consonants. I think it's non-intuitive to both Japanese and English speakers.

Portuguese-style romaji was used in the 16th century, and it included some diacritics. Historically, there were also French-, Dutch-, and German-style systems (see a table in the middle of this page). I don't know about them, but I believe they are not actively used today, anyway. For example, tsunami is spelled as tsunami in all these languages.