JEP-400 was implemented by JDK18-b13.
After JDK18-b13, garbled character was displayed by following code on Japanese Windows' command prompt.

System.out.println("\u3042")

Japanese "A" should be displayed, but garbled character was displayed.
See jshell-image01.png

Also saved jshell command list did not work as expected if Japanese character was there.
See jshell-image02.png

Following issue has some information
8274544: Langtools command's usage were garbled on Japanese Windows #5771
https://github.com/openjdk/jdk/pull/5771