Ok, here are System preferences panel window. One is Japanese language and another is English language.

Sorry It was my misunderstanding.
Even I unchecked "Update change rates" in Currencies in preferences window, I can't input Japanese ￥ correctly.

I had same problem.
However if I unchecked "Update change rates" in Currencies in preferences window in iCompta, I can input Japanese ￥ correctly.
Is that you suggest to input in Japanese currencies ?