plugin.txt's formatting is odd and causes there to be no spacing between "Label to UST" and "execute" so utau's drop down menu for plugins read as "Label to USTexecute" and does not execute instead of reading as "Label to UST" and executing.

rewriting the plugin.txt fixes the error but some (like me) may not catch it at first

I ran the plugin after changing the bpm and saving the ust, then immediately got this

I have check the corresponding lab file, with the same name as the ust, for empty labels and find none. I tried adding a rest in the ust and then run the plugin after clicking on it, still the same error. lab2ust have not asked me for the lab or frq files yet.

Japanese datasets are incorrectly detected as another language if capitalized phonemes exist.
For NNSVS Japanese datasets (and Japanese speech datasets in general, somewhat), capitalized vowel phonemes represent unvoiced vowels.

May I suggest updating the detection?

    label_lang = input('Is dataset Japanese? [y/n] ')
    if label_lang.lower() == 'y':
        jpn = True
    else:
        jpn = False

May I also suggest adding the capitalized phonemes to the vowel list and change line 129 to something like not in ('pau', 'sil') else 'R' since pau and sil are used interchangeably?

Thank you.