eSpeak-ng says "Chinese letter" or "Japanese letter" for Japanese characters it doesn't support, causing quality of `dtw` alignment and some synthesis engines to be degraded for Japanese

[rotemdan]

The issue has been in espeak-ng for a very long time and cannot be worked around. espeak-ng doesn't support Kanji characters, and possibly other characters used in Japanese.

To align Japanese text, the Whisper-based alignment engines (whisper and dtw-ra) are still usable.