most japanese keyboards have a "半角/全角 キー" to switch between hiragana and English input languages.
it worked fine before, but after 1.13 or 1.14, it stopped working under certain conditions.

Reproduction Procedure:
(1) Open the chat and make sure you can type Japanese.
(2) Open an application such as Notepad, which allows you to enter multi-column text, and enter some characters.
(3) When I open the chat again, the keys are inoperative and I can only type in English.

No matter how many times i press it, was not return me any responses. Forcing the input assistant to start won't fix it.

theres no other way to type Japanese under this situation but to copy and paste text from Notepad.
Strangely enough, when I press that 半角/全角 key when entering multi-column text, such as command block with an expanded input field, it works as if nothing happened.
however, even though it can be cured, theres no solution for featured server such as Hive, which requires communication.
it was working fine before, so there's no reason it shouldn't be so now.
i hope it will be fixed sooner.