The modern Japanese language is based primarily on the western dialects around the Kinki region.
- Middle Japanese /P/ remained /P/ rather than becoming /h/ as *here*.
- Contact with languages such as Dutch and English caused the borrowing of the phoneme /h/. This was initially written with the k-row kana. Eventually a distinction was felt to be necessary between /k/ and /h~x/. This was achieved by borrowing a set of hentaigana (old alternate kana) for the k-row to mark /h~x/.
- The phoneme /l/ was borrowed, written with former hentaigana for the r-row.
- /s/ is pronounced /S/ before /i/ and /e/.
- /kwa/ and /gwa/ were retained.
- The pairs /dZ/-/Z/ and /dz/-/z/ have merged.
- Intervocalic moraic n lost; following vowel acquires /n/ onset (e.g., kan'in -> kannin)
- /g/ pronounced [N] intervocallically
- Finally, syllable structure was altered slightly, to incorporate syllable-final (but still moraic) /l/, /P/, and /s/, written with smaller versions of lu, fu and su
At the time of Japanese-European contact, Japanese phonology still made the /dZi~Zi/ and /dzu~zu/ contrasts, in addition to having /kwa/ and /gwa/ syllables distinct from /ka/ and /ga/. There was also a contrast between /O:/ and /o:/. Modern /h/ was still pronounced /P/. The syllables /e/ and /o/ were [je] and [wo]. Modern /se/ was /Se/, as it still is in many dialects. I suspect that Japanese *there* would've retained /Se/ as the standard, as Japan *there* would retain the Kyoto region as its political center, instead of moving to the Kantō region, which was a center of /se/ usage (a Portuguese description of Japanese, referring to the use of /se/, wrote that "people in Qvantô are notorious for such mispronunciations")
Portuguese Romanization appears to have been as follows:
- Ô for /o:/
- Ó for /O:/
- C for /k/
- qi, qe, qva for /ki/, /ke/, /kwa/
- x for /S/
- zu for /zu/
- gi for /Zi/
- dzu, zzu for /dzu/
- tçu for /tsu/
- ji for /dZi/
- v for /w/
I do not know how they wrote /gi/ and /ge/.
I don't suggest that the Portuguese version be adopted in toto. But, some of it may be adopted. A question arises - how conservative would romanization be? I see no reason, for example, to retain the /P/ pronunciation. However, would F be kept as the romanization, or would it change at some point to reflect the new pronunciation? And how would historic names be affected if it was changed? Would they continue being spelled in Western languages with F or with the new H?
By the late 17th century, a standard romanization began to take shape. It evolved gradually, as initially numerous systems existed. The standard came to be:
- /O:/ was written Ó
- Long vowels (other than /O:/) were written with circumflex
- /k/ was written k
- /kw/ was written Qu
- /g/ was written G (Gh before /i/ and /e/ sometimes remained)
- /S/ was written X or sometimes Sh
- /Z/ was written J
- /ts/ was written ç
- /tS/ was written Ch
- /dZ/ was written Dj
- /P/ was written F
- /j/ was written Y
- /w/ was written W
- Syllabic n was ignored, or distinguished with a hyphen
- The syllables /e/ and /o/ (that is, /e/ and /o/ without onsets) were written Ye and Wo, reflecting the pronunciation of the time.
Similar to the early romanization, with the following exceptions
- Long vowels marked with circumflex, ó and ô no longer distinguished (phonetic merger)
- /S/ is consistently written x
- /dZ/ is written J
- /ts/ is written c
- [N] written ng
- [Ng] written nng