Due to a misconfiguration when uploading the Korean version, there was a temporary issue where Japanese could not be selected.
This issue has now been fixed, and Japanese is available again as expected.
The problem was caused by both the Korean and Japanese versions being set to “All Languages” in Steamworks.
We’ve corrected the settings to match the appropriate languages, and everything is working fine now.
We sincerely apologize for the inconvenience.
And a big thank-you to everyone who reported the issue!