The operating system region and language needs to be set to Japanese.

RichTextBox seems to have several issues with Japanese, but being locked from visibility or edit is the biggest one.

To recreate, start typing in Japanese, push the "right" arrow after selecting the IME option desired, then hit "spacebar." This seems to duplicate the text, then when trying to continue to type into the text field the text is no longer visible (yet the IME does display).

The native WPF RichTextBox has no issues (and also supports partial selection, etc.).

I've attached a video to show the behavior with 2025 Q1 telerik.

*note:* This is on a machine with NVIDIA graphics. I mention this as there may be some issues with RichTextBox and the hardware... When I'm in a virtual machine with a completely Japanese environment and virtual graphics driver, there is NO text visible at all when trying to type into the RichTextBox. Works fine with other controls and wpf RichTextBox.

RadRichTextBox: Exception when one parses styles that contain specific (German) characters.

Having a table, for example, with empty cells, executing the TabBackwardsCommand does not move the caret to the previous cell of the row.

If I select multiple Paragraphs and TabForward, all paragraphs will be indented by [indent value]*[selected paragraphs]

When RadRichTextBox for WPF is hosted in a WinForms application (through ElementHost), typing with Japanese IME duplicates the typed letters, which makes the control unusable with the default behavior.

Possible workaround: Create custom caret. There are some suggestions in this forum thread: https://www.telerik.com/forums/richtextbox-doesn't-support-japanese-ime-when-hosted-in-winforms