diff --git a/configure b/configure
index c807295..1454d64 100755
--- a/configure
+++ b/configure
@@ -15773,7 +15773,9 @@ else
 fi
 
 SRC_MENU=
-if test "x$have_gtk" = xyes ; then
+if test "x$is_emscripten" = xyes; then
+  SRC_MENU="menu_emscripten.c"
+elif test "x$have_gtk" = xyes ; then
   SRC_MENU="menu.c menu_callback.c menu_gui.c s39init.c"
 else
   SRC_MENU="menu_null.c"
diff --git a/configure.ac b/configure.ac
index 777afe8..caaedb1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -164,7 +164,9 @@ dnl fi
 
 AM_CONDITIONAL(HAVE_GTK, test "x$have_gtk" = xyes)
 SRC_MENU=
-if test "x$have_gtk" = xyes ; then
+if test "x$is_emscripten" = xyes; then
+  SRC_MENU="menu_emscripten.c"
+elif test "x$have_gtk" = xyes ; then
   SRC_MENU="menu.c menu_callback.c menu_gui.c s39init.c"
 else
   SRC_MENU="menu_null.c"
diff --git a/src/menu_emscripten.c b/src/menu_emscripten.c
new file mode 100644
index 0000000..deb934f
--- /dev/null
+++ b/src/menu_emscripten.c
@@ -0,0 +1,78 @@
+/*
+ * menu_emscripten.c  menu implementation for Emscripten
+ *
+ * Copyright (C) 2017 <KichikuouChrome@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+*/
+#include "config.h"
+
+#include <stdio.h>
+#include <emscripten.h>
+
+#include "portab.h"
+#include "menu.h"
+
+void menu_open(void) {
+	return;
+}
+
+void menu_quitmenu_open(void) {
+	return;
+}
+
+boolean menu_inputstring(INPUTSTRING_PARAM *p) {
+	static char buf[256];
+	int ok = EM_ASM_({
+			var r = xsystem35.shell.inputString(UTF8ToString($0), UTF8ToString($1), $2);
+			if (r) {
+				stringToUTF8(r, $3, $4);
+				return 1;
+			}
+			return 0;
+		}, p->title, p->oldstring, p->max, buf, sizeof buf);
+	if (ok)
+		p->newstring = buf;
+	else
+		p->newstring = p->oldstring;
+	return ok ? TRUE : FALSE;
+}
+
+boolean menu_inputstring2(INPUTSTRING_PARAM *p) {
+	p->newstring = p->oldstring;
+	return TRUE;
+}
+
+boolean menu_inputnumber(INPUTNUM_PARAM *p) {
+	p->value = p->def;
+	return TRUE;
+}
+
+void menu_msgbox_open(char *msg) {
+	return;
+}
+
+void menu_init(void) {
+	return;
+}
+
+void menu_widget_reinit(boolean reset_colortmap) {
+	return;
+}
+
+void menu_gtkmainiteration() {
+	return;
+}
diff --git a/src/utfsjis.c b/src/utfsjis.c
index 3d6525c..53bda7b 100644
--- a/src/utfsjis.c
+++ b/src/utfsjis.c
@@ -67,9 +67,55 @@ BYTE *sjis2utf(BYTE *src) {
 	return dst;
 }
 
+static int unicode_to_sjis(int u) {
+	for (int b1 = 0x80; b1 <= 0xff; b1++) {
+		if (b1 >= 0xa0 && b1 <= 0xdf)
+			continue;
+		for (int b2 = 0x40; b2 <= 0xff; b2++) {
+			if (u == s2u[b1 - 0x80][b2 - 0x40])
+				return b1 << 8 | b2;
+		}
+	}
+	return 0;
+}
+
 BYTE *utf2sjis(BYTE *src) {
-	printf("%s not implemented\n", __func__);
-	return strdup(src);
+	BYTE* dst = malloc(strlen(src) + 1);
+	BYTE* dstp = dst;
+
+	while (*src) {
+		if (*src <= 0x7f) {
+			*dstp++ = *src++;
+			continue;
+		}
+
+		int u;
+		if (*src <= 0xdf) {
+			u = (src[0] & 0x1f) << 6 | (src[1] & 0x3f);
+			src += 2;
+		} else if (*src <= 0xef) {
+			u = (src[0] & 0xf) << 12 | (src[1] & 0x3f) << 6 | (src[2] & 0x3f);
+			src += 3;
+		} else {
+			*dstp++ = '?';
+			do src++; while ((*src & 0xc0) == 0x80);
+			continue;
+		}
+
+		if (u > 0xff60 && u <= 0xff9f) {
+			*dstp++ = u - 0xff60 + 0xa0;
+		} else {
+			int c = unicode_to_sjis(u);
+			if (c) {
+				*dstp++ = c >> 8;
+				*dstp++ = c & 0xff;
+			} else {
+				*dstp++ = '?';
+			}
+		}
+	}
+	*dstp = '\0';
+	return dst;
 }
 
 /* src 内に半角カナもしくはASCII文字があるかどうか */