ah my friend you misunderstood me - not that you could not post in Japanese only that we would rather not mix languages in the same database...that has been tried before and it gets rather confusing for all concerned.
We run the forum on a platform that uses UTF-8 encoding from front to back so entering the characters will work, as you see..
Former member of The Document Foundation
Former member of Apache OpenOffice PMC
LibreOffice on Ubuntu 18.04