diff --git a/samples/AzureADB2CAuth/auth-frontend/index.html b/samples/AzureADB2CAuth/auth-frontend/index.html
index d9ce66a4a..a76b582fb 100644
--- a/samples/AzureADB2CAuth/auth-frontend/index.html
+++ b/samples/AzureADB2CAuth/auth-frontend/index.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html lang="en">
+<html lang="ja">
   <head>
     <meta charset="UTF-8" />
     <link rel="icon" href="/favicon.ico" />
diff --git a/samples/Dressca/dressca-frontend/index.html b/samples/Dressca/dressca-frontend/index.html
index d9ce66a4a..a76b582fb 100644
--- a/samples/Dressca/dressca-frontend/index.html
+++ b/samples/Dressca/dressca-frontend/index.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html lang="en">
+<html lang="ja">
   <head>
     <meta charset="UTF-8" />
     <link rel="icon" href="/favicon.ico" />
diff --git a/samples/monorepo-frontend/apps/app-a/index.html b/samples/monorepo-frontend/apps/app-a/index.html
index a88854489..72386bbe8 100644
--- a/samples/monorepo-frontend/apps/app-a/index.html
+++ b/samples/monorepo-frontend/apps/app-a/index.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html lang="en">
+<html lang="ja">
   <head>
     <meta charset="UTF-8">
     <link rel="icon" href="/favicon.ico">
diff --git a/samples/monorepo-frontend/modules/component/index.html b/samples/monorepo-frontend/modules/component/index.html
index 143557b52..13f6448b1 100644
--- a/samples/monorepo-frontend/modules/component/index.html
+++ b/samples/monorepo-frontend/modules/component/index.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html lang="en">
+<html lang="ja">
   <head>
     <meta charset="UTF-8" />
     <link rel="icon" type="image/svg+xml" href="/vite.svg" />
