Why Is Windows Security in English on a Japanese Windows 11? The Cause and the Fix

Hi everyone, it's Shiichan! Today isn't a new feature, it's a small-but-annoying display bug that's worth knowing about.

What was announced?

JP Windows Support, the blog run by Microsoft Japan's Windows support team, published a post about an issue where, right after a clean install of Windows 11 version 24H2, 25H2, or 26H1, Explorer and Settings display in Japanese as expected but the Windows Security app shows some or all of its text in English. It's purely a display issue and doesn't affect how protection features actually work, but the mismatch is jarring.

The story so far

The cause traces back to how the Windows 11 install media and images were built: the Japanese display resources for the Windows Security app simply weren't included. Since the OS-wide language files and each app's own language resources are managed separately, the app fell back to its English resources while the rest of the system stayed in Japanese.

What changes

Installing update KB5007651 (a Windows Security platform update) fixes the display so it shows Japanese correctly. If you're deploying multiple machines in an organization, it's worth adding KB5007651 to your standard post-imaging setup steps.

Dive Deep

Two ways to apply the fix are described.

• Via Windows Update: close Windows Security, open Settings > Windows Update, run "Check for updates," install KB5007651 when it appears, restart if needed, and reopen Windows Security to confirm
• Manually via the Microsoft Update Catalog: close Windows Security, search for KB5007651 in the Microsoft Update Catalog, download the file matching your device's architecture (version 10.0.29628.1000 or later as of this writing), run the installer as administrator, and confirm the display

KB5007651 keeps the same KB number across versions, so make sure you're grabbing the latest one each time. It's also distributable via WSUS, so it fits into existing internal deployment pipelines.

If the fix doesn't resolve things, check the scope of the English text, the Windows version and build number via winver, the Windows Security app version, and the system-wide display language setting in Settings. For environments without internet access, download the latest version from the Microsoft Update Catalog ahead of time and distribute it internally.

Wrap-up

• A clean install of Windows 11 (24H2/25H2/26H1) can leave Windows Security displaying in English while the rest of the OS is in Japanese
• The cause is missing Japanese display resources in the install image
• Applying update KB5007651 via Windows Update or the Update Catalog resolves it
• Admins deploying multiple machines should add KB5007651 to their standard post-imaging setup