diff --git a/vba_code_common.bas b/vba_code_common.bas
index 337e86d..88f18f8 100644
--- a/vba_code_common.bas
+++ b/vba_code_common.bas
@@ -151,3 +151,25 @@ Function ReadCSVFileWithUtf8(ByVal filePath As String) As Variant
     
     ReadCSVFileWithUtf8 = Split(textContent, vbLf)
 End Function
+
+Function ReadCSVFile(ByVal filePath As String, Optional ByVal charset As String = "shift_jis") As Variant
+    If filePath = "" Then
+        ReadCSVFile = Array()
+        Exit Function
+    End If
+    
+    Dim stream As Object
+    Dim textContent As String
+    
+    Set stream = CreateObject("ADODB.Stream")
+    With stream
+        .Type = 2
+        .Charset = charset
+        .Open
+        .LoadFromFile filePath
+        textContent = .ReadText
+        .Close
+    End With
+    
+    ReadCSVFile = Split(textContent, vbLf)
+End Function
diff --git a/vba_code_kotsu_master.bas b/vba_code_kotsu_master.bas
index daede6e..9d78e19 100644
--- a/vba_code_kotsu_master.bas
+++ b/vba_code_kotsu_master.bas
@@ -19,7 +19,7 @@ Sub Z1_ImportMasterDetailData()
     If filePath = "" Then Exit Sub
     
     ' Step 2: Read CSV
-    lines = ReadCSVFileWithUtf8(filePath)
+    lines = ReadCSVFile(filePath, "utf-8")
     
     ' Step 3: Validate column count
     If Not ValidateCSVColumnCount(lines, 7) Then Exit Sub