SOLVED: "Japanese IME not ready yet" & "Downloading language dictionary" trouble

If you are having one of these issues described below on Windows 10 computers, try my solution. It cleared up both issues (on two separate machines).

1. When you try to type in Japanese, you are told "Japanese IME is not ready yet."

2. When you try to type in Japanese, you are told "Downloading language dictionary" but it never finishes.

CAUSE:

The two machines were missing dictionary files. The error messages make sense.

SOLUTION:

Find a machine with working Japanese IME and copy the dictionary files. You may not have a working machine, so I have the files here.

Unzip and copy these files to c:/Windows/IME/IMEJP/DICTS, and that's it. No reboot necessary.