diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 693040b..6720097 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -5,6 +5,7 @@ project(System3 LANGUAGES CXX)
 set(SRC_COMMON
   sdlmain.cpp
   fileio.cpp
+  utfsjis.cpp
   sys/ags.cpp
   sys/ags_cursor.cpp
   sys/ags_draw.cpp
diff --git a/src/linux/nact_linux.cpp b/src/linux/nact_linux.cpp
index b160377..56c2b22 100644
--- a/src/linux/nact_linux.cpp
+++ b/src/linux/nact_linux.cpp
@@ -1,13 +1,8 @@
 #include <stdio.h>
 #include "nact.h"
+#include "utfsjis.h"
 #ifdef __EMSCRIPTEN__
 #include <emscripten.h>
-
-extern "C" {
-// ags_text.cpp
-char* sjis2utf(char* src);
-char* utf2sjis(char* src);
-}
 #endif
 
 void NACT::text_dialog()
diff --git a/src/sys/ags_text.cpp b/src/sys/ags_text.cpp
index 33204ac..008bec2 100644
--- a/src/sys/ags_text.cpp
+++ b/src/sys/ags_text.cpp
@@ -6,19 +6,10 @@
 
 #include <string.h>
 #include "ags.h"
-#include "s2utbl.h"
+#include "utfsjis.h"
 
 static bool antialias = false;
 
-inline uint16 sjis_to_unicode(uint16 code)
-{
-	if (code >= 0xa0 && code <= 0xdf)
-		return 0xff60 + code - 0xa0;
-	if (code < 0x100)
-		return code;
-	return s2u[(code >> 8) - 0x80][(code & 0xff) - 0x40];
-}
-
 void AGS::draw_text(char string[])
 {
 	int p = 0;
@@ -539,93 +530,4 @@ void ags_setAntialiasedStringMode(int on) {
 	antialias = on != 0;
 }
 
-#ifdef __EMSCRIPTEN__
-char* sjis2utf(char* str) {
-	unsigned char* src = (unsigned char*)str;
-	unsigned char* dst = (unsigned char*)malloc(strlen(str) * 3 + 1);
-	unsigned char* dstp = dst;
-
-	while (*src) {
-		if (*src <= 0x7f) {
-			*dstp++ = *src++;
-			continue;
-		}
-
-		int c;
-		if (*src >= 0xa0 && *src <= 0xdf) {
-			c = 0xff60 + *src - 0xa0;
-			src++;
-		} else {
-			c = s2u[*src - 0x80][*(src+1) - 0x40];
-			src += 2;
-		}
-
-		if (c <= 0x7f) {
-			*dstp++ = c;
-		} else if (c <= 0x7ff) {
-			*dstp++ = 0xc0 | c >> 6;
-			*dstp++ = 0x80 | (c & 0x3f);
-		} else {
-			*dstp++ = 0xe0 | c >> 12;
-			*dstp++ = 0x80 | (c >> 6 & 0x3f);
-			*dstp++ = 0x80 | (c & 0x3f);
-		}
-	}
-	*dstp = '\0';
-	return (char*)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;
-}
-
-char* utf2sjis(char* str) {
-	unsigned char* src = (unsigned char*)str;
-	unsigned char* dst = (unsigned char*)malloc(strlen(str) + 1);
-	unsigned char* 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 (char*)dst;
-}
-#endif
-
 }
diff --git a/src/utfsjis.cpp b/src/utfsjis.cpp
new file mode 100644
index 0000000..d0bce1d
--- /dev/null
+++ b/src/utfsjis.cpp
@@ -0,0 +1,104 @@
+#include <stdlib.h>
+#include <string.h>
+#include "utfsjis.h"
+
+namespace {
+#include "s2utbl.h"
+
+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;
+}
+
+} // namespace
+
+uint16 sjis_to_unicode(uint16 code)
+{
+	if (code >= 0xa0 && code <= 0xdf)
+		return 0xff60 + code - 0xa0;
+	if (code < 0x100)
+		return code;
+	return s2u[(code >> 8) - 0x80][(code & 0xff) - 0x40];
+}
+
+char* sjis2utf(char* str) {
+	unsigned char* src = (unsigned char*)str;
+	unsigned char* dst = (unsigned char*)malloc(strlen(str) * 3 + 1);
+	unsigned char* dstp = dst;
+
+	while (*src) {
+		if (*src <= 0x7f) {
+			*dstp++ = *src++;
+			continue;
+		}
+
+		int c;
+		if (*src >= 0xa0 && *src <= 0xdf) {
+			c = 0xff60 + *src - 0xa0;
+			src++;
+		} else {
+			c = s2u[*src - 0x80][*(src+1) - 0x40];
+			src += 2;
+		}
+
+		if (c <= 0x7f) {
+			*dstp++ = c;
+		} else if (c <= 0x7ff) {
+			*dstp++ = 0xc0 | c >> 6;
+			*dstp++ = 0x80 | (c & 0x3f);
+		} else {
+			*dstp++ = 0xe0 | c >> 12;
+			*dstp++ = 0x80 | (c >> 6 & 0x3f);
+			*dstp++ = 0x80 | (c & 0x3f);
+		}
+	}
+	*dstp = '\0';
+	return (char*)dst;
+}
+
+char* utf2sjis(char* str) {
+	unsigned char* src = (unsigned char*)str;
+	unsigned char* dst = (unsigned char*)malloc(strlen(str) + 1);
+	unsigned char* 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 (char*)dst;
+}
diff --git a/src/utfsjis.h b/src/utfsjis.h
new file mode 100644
index 0000000..e5c84ec
--- /dev/null
+++ b/src/utfsjis.h
@@ -0,0 +1,10 @@
+#ifndef _UTFSJIS_H_
+#define _UTFSJIS_H_
+
+#include "common.h"
+
+uint16 sjis_to_unicode(uint16 code);
+char* sjis2utf(char* src);
+char* utf2sjis(char* src);
+
+#endif // _UTFSJIS_H_