diff --git a/src/protocol/renderer_command.proto b/src/protocol/renderer_command.proto
index f366303c9..1758479a6 100644
--- a/src/protocol/renderer_command.proto
+++ b/src/protocol/renderer_command.proto
@@ -76,6 +76,9 @@ message RendererCommand {
     optional Point top_left = 2;
     optional uint32 line_height = 3;
     optional Rectangle document_area = 4;
+    // A quick solution for vertical writing support.
+    // Strictly speaking, this is not part of IMECHARPOSITION in IMM32.
+    optional bool vertical_writing = 5;
   }
 
   // Visual information about mode indicator.
diff --git a/src/renderer/win32/win32_renderer_util.cc b/src/renderer/win32/win32_renderer_util.cc
index 317ae96cc..71416baec 100644
--- a/src/renderer/win32/win32_renderer_util.cc
+++ b/src/renderer/win32/win32_renderer_util.cc
@@ -763,9 +763,12 @@ double LayoutManager::GetScalingFactor(HWND window_handle) const {
 
 LayoutManager::WritingDirection LayoutManager::GetWritingDirection(
     const commands::RendererCommand_ApplicationInfo &app_info) {
-  // TODO(https://github.com/google/mozc/issues/362): Implement this for TSF.
-  // When fixing this, we also need to update Chromium.
-  //   https://chromium-review.googlesource.com/c/chromium/src/+/4023235
+  const commands::RendererCommand::CharacterPosition &composition_target =
+      app_info.composition_target();
+  if (composition_target.has_vertical_writing()) {
+    return composition_target.vertical_writing() ? VERTICAL_WRITING
+                                                 : HORIZONTAL_WRITING;
+  }
   return WRITING_DIRECTION_UNSPECIFIED;
 }
 
diff --git a/src/win32/tip/tip_range_util.cc b/src/win32/tip/tip_range_util.cc
index 9231b8f3a..45d3c3dfa 100644
--- a/src/win32/tip/tip_range_util.cc
+++ b/src/win32/tip/tip_range_util.cc
@@ -55,6 +55,13 @@ constexpr GUID kGuidPropInputscope = {
     0x4a5b,
     {0x9a, 0xf6, 0x59, 0x2a, 0x59, 0x5c, 0x77, 0x8d}};
 
+// TSATTRID_Text_VerticalWriting
+constexpr GUID kGuidAttrIdTextVerticalWriting = {
+    0x6bba8195,
+    0x046f,
+    0x4ea9,
+    {0xb3, 0x11, 0x97, 0xfd, 0x66, 0xc4, 0x27, 0x4b}};
+
 HRESULT GetReadOnlyAppProperty(ITfRange *range, TfEditCookie read_cookie,
                                const GUID &guid, VARIANT *variant_addr) {
   HRESULT result = S_OK;
@@ -214,6 +221,26 @@ HRESULT TipRangeUtil::GetInputScopes(ITfRange *range, TfEditCookie read_cookie,
   return S_OK;
 }
 
+HRESULT TipRangeUtil::IsVerticalWriting(ITfRange *range,
+                                        TfEditCookie read_cookie,
+                                        bool *vertical_writing) {
+  if (vertical_writing == nullptr) {
+    return E_FAIL;
+  }
+  *vertical_writing = false;
+
+  wil::unique_variant variant;
+  HRESULT result = GetReadOnlyAppProperty(range,
+                                          read_cookie,
+                                          kGuidAttrIdTextVerticalWriting,
+                                          variant.reset_and_addressof());
+  if (FAILED(result)) {
+    return result;
+  }
+  *vertical_writing = (variant.vt == VT_BOOL && variant.boolVal != 0);
+  return S_OK;
+}
+
 bool TipRangeUtil::IsRangeCovered(TfEditCookie edit_cookie,
                                   ITfRange *range_test, ITfRange *range_cover) {
   HRESULT result = S_OK;
diff --git a/src/win32/tip/tip_range_util.h b/src/win32/tip/tip_range_util.h
index e46644f78..f7b97476a 100644
--- a/src/win32/tip/tip_range_util.h
+++ b/src/win32/tip/tip_range_util.h
@@ -69,6 +69,11 @@ class TipRangeUtil {
   static HRESULT GetInputScopes(ITfRange *range, TfEditCookie read_cookie,
                                 std::vector<InputScope> *input_scopes);
 
+  // Retrieves whether the specified |range| is for vertical writing or not.
+  // Returns the general result code.
+  static HRESULT IsVerticalWriting(ITfRange *range, TfEditCookie read_cookie,
+                                   bool *vertical_writing);
+
   // Checks whether or not |range_test| becomes a subset of |range_cover|.
   static bool IsRangeCovered(TfEditCookie edit_cookie, ITfRange *range_test,
                              ITfRange *range_cover);
diff --git a/src/win32/tip/tip_ui_handler_conventional.cc b/src/win32/tip/tip_ui_handler_conventional.cc
index 76d1e1a5a..56e027e89 100644
--- a/src/win32/tip/tip_ui_handler_conventional.cc
+++ b/src/win32/tip/tip_ui_handler_conventional.cc
@@ -277,10 +277,39 @@ bool FillCharPosition(TipPrivateContext *private_context, ITfContext *context,
       app_info->mutable_composition_target();
   composition_target->set_position(0);
 
+  bool vertical_writing = false;
+  if (SUCCEEDED(TipRangeUtil::IsVerticalWriting(
+          target_range.get(), read_cookie, &vertical_writing))) {
+    composition_target->set_vertical_writing(vertical_writing);
+  }
+
   RendererCommand::Point *point = composition_target->mutable_top_left();
-  point->set_x(text_rect.left);
-  point->set_y(text_rect.top);
-  composition_target->set_line_height(text_rect.bottom - text_rect.top);
+  if (vertical_writing) {
+    // [Vertical Writing]
+    //    |
+    //    +-----< (pt)
+    //    |     |
+    //    |-----+
+    //    | (cLineHeight)
+    //    |
+    //    |
+    //    v
+    //   (Base Line)
+    point->set_x(text_rect.right);
+    point->set_y(text_rect.top);
+    composition_target->set_line_height(text_rect.right - text_rect.left);
+  } else {
+    // [Horizontal Writing]
+    //    (pt)
+    //     v_____
+    //     |     |
+    //     |     | (cLineHeight)
+    //     |     |
+    //   --+-----+---------->  (Base Line)
+    point->set_x(text_rect.left);
+    point->set_y(text_rect.top);
+    composition_target->set_line_height(text_rect.bottom - text_rect.top);
+  }
 
   RendererCommand::Rectangle *area =
       composition_target->mutable_document_area();