diff --git a/scim-wnn/src/romkan.cpp b/scim-wnn/src/romkan.cpp
index 6e3282f..d61cf4d 100644
--- a/scim-wnn/src/romkan.cpp
+++ b/scim-wnn/src/romkan.cpp
@@ -56,7 +56,7 @@
 void Romkan::setPos(int p)
 {
     if (p < 0) p = 0;
-    if (p > getTextLength()) p = getTextLength();
+    else if (p > getTextLength()) p = getTextLength();
     pos = p;
     buf.clear();
 }
@@ -80,7 +80,7 @@
     buf += k;
     String s;
     s = k;
-    text = text.substr(0,pos)  + utf8_mbstowcs(s) + text.substr(pos ++);
+    text = text.substr(0,pos) + utf8_mbstowcs(s) + text.substr(pos ++);
     //return(text);
     return(eval());
 }
@@ -175,7 +175,7 @@
  */
 void Romkan::backspace()
 {
-    if (getPos() == 0);
+    if (getPos() == 0) return;
     text = text.substr(0,pos - 1) + text.substr(pos);
     setPos(pos - 1);
     // BS�Ͼ��Хåե���BS���륾��
@@ -252,8 +252,8 @@
  */
 bool Romkan::keyEventHook(const KeyEvent &key)
 {
-    if (text.empty()) return(false);
-    if (text.substr(pos - 1,1) == utf8_mbstowcs("Z")) {
+    if (!buf.length()) return(false);
+    if (buf[buf.length() - 1] == 'Z') {
         if (key.code == SCIM_KEY_space) {
             insert(key.get_ascii_code());
             return(true);
diff --git a/scim-wnn/src/scim_wnn_imengine.cpp b/scim-wnn/src/scim_wnn_imengine.cpp
index b749408..f70203b 100644
--- a/scim-wnn/src/scim_wnn_imengine.cpp
+++ b/scim-wnn/src/scim_wnn_imengine.cpp
@@ -66,10 +66,6 @@
 static ConfigPointer _scim_config;
 
 extern "C" {
-    // ����Ǥ��礦��
-    // KDE�ʤ󤫤Ǥ�Ȥ��Ƥ�ưŪ���ǥ��󥰤ξ�����
-    // C��󥱡����Ǵؿ�̾���ꤵ���ơ����ä��饤�󥹥��󥹺��äġ����졣
-    // ���ݤ���ͤ����ޤ��̤��ɤ����ɤ���
     void scim_module_init (void)
     {
     }
@@ -106,12 +102,10 @@
 }
 
 WnnFactory::WnnFactory(const WideString & name, const String & languages) {
-    // ʸ�������¤���
     if (name.length () <= 8)
         m_name = name;
     else
         m_name.assign (name.begin (), name.begin () + 8);
-    // �Ȥꤢ�������ܸ�Ķ��Ǹ��ꤷ�����ȥ�����
     if (languages == String ("default"))
         set_languages (String (_("ja_JP")));
     else
@@ -120,43 +114,36 @@
 
 WideString WnnFactory::get_name () const
 {
-    // ̾�����֤��Τ͡�utf8_mbstowcs(_("Wnn"))�ǡ�
     return m_name;
 }
 
 WideString WnnFactory::get_authors () const
 {
-    // AUTHER�͡�
     return utf8_mbstowcs (String (_("(C) 2004 TAM(Teppei Tamra) <tam-t@par.odn.ne.jp>")));
 }
 
 WideString WnnFactory::get_credits () const
 {
-    // CREDIT�͡��Ȥꤢ�������ǡ�
     return WideString ();
 }
 
 WideString WnnFactory::get_help () const
 {
-    // HELP��񤫤ʤ��ȥ���ʤΤ͡�
     return utf8_mbstowcs (String (_("SCIM-WNN HELP")));
 }
 
 String WnnFactory::get_uuid () const
 {
-    // uuidgená���Ƽ��̤ȡ���ˡ����ʤ�ʤ�Ǥ�褵�������ɤ⡣
     return String ("c069395a-d62f-4a77-8229-446e44a99976");
 }
 
 String WnnFactory::get_icon_file () const
 {
-    // �����������ꡣ���ʤ��Ȥ͡�
     return String (SCIM_WNN_ICON_FILE);
 }
 
 IMEngineInstancePointer WnnFactory::create_instance (const String& encoding, int id)
 {
-    // �ºݤ˥��󥹥��󥹤��롣
     return new WnnInstance (this, encoding, id);
 }
 
@@ -185,7 +172,6 @@
 }
 
 
-// �� �� ý ��
 // ��ʪ��
 
 
@@ -201,7 +187,6 @@
     m_iconv.set_encoding ("EUC-JP");
 
     // �ǥե���ȥ������ꡣ
-    // ����ե����뤫���ɤ�褦�ˤ��Ƥ��ˤ礴�ˤ硣
     scim_string_to_key_list(k_conversion_start,
         _scim_config->read(String(SCIM_CONFIG_WNN_KEY_CONVERSION_START),
             String(SCIM_DEFAULT_WNN_KEY_CONVERSION_START)));
@@ -312,6 +297,7 @@
             return(false);
         }
         k_backward.comp(key) ? m_rk.setPos(m_rk.getPos() - 1) : m_rk.setPos(m_rk.getPos() + 1);
+        update_preedit_string(m_rk.getText());
         update_preedit_caret(m_rk.getPos());
         return(true);
     } else
@@ -523,8 +509,8 @@
 
 void WnnInstance::move_preedit_caret (unsigned int pos)
 {
-    if (!m_conversion) m_rk.setPos(pos);
-    update_preedit_caret(pos);
+    //if (!m_conversion) m_rk.setPos(pos);
+    //update_preedit_caret(pos);
 }
 
 void WnnInstance::select_candidate (unsigned int item)