diff --git a/src/encoding.cpp b/src/encoding.cpp
index e652174..c02109b 100644
--- a/src/encoding.cpp
+++ b/src/encoding.cpp
@@ -11,12 +11,12 @@ namespace {
 
 class SjisEncoding : public Encoding {
 public:
-	int mblen(const unsigned char* s)
+	int mblen(unsigned char first_byte) override
 	{
-		return is_2byte(*s) ? 2 : 1;
+		return is_2byte(first_byte) ? 2 : 1;
 	}
 
-	int next_codepoint(const unsigned char** s)
+	int next_codepoint(const unsigned char** s) override
 	{
 		int code = *(*s)++;
 		if (is_2byte(code))
@@ -24,7 +24,7 @@ public:
 		return sjis_to_unicode(code);
 	}
 
-	char* fromUtf8(const char* str)
+	char* fromUtf8(const char* str) override
 	{
 		unsigned char* src = (unsigned char*)str;
 		unsigned char* dst = (unsigned char*)malloc(strlen(str) + 1);
@@ -65,7 +65,7 @@ public:
 		return (char*)dst;
 	}
 
-	char* toUtf8(const char* str)
+	char* toUtf8(const char* str) override
 	{
 		unsigned char* src = (unsigned char*)str;
 		unsigned char* dst = (unsigned char*)malloc(strlen(str) * 3 + 1);
@@ -138,18 +138,18 @@ private:
 
 class Utf8Encoding : public Encoding {
 public:
-	int mblen(const unsigned char* s)
+	int mblen(unsigned char first_byte) override
 	{
-		if (*s <= 0xbf)
+		if (first_byte <= 0xbf)
 			return 1;
-		if (*s <= 0xdf)
+		if (first_byte <= 0xdf)
 			return 2;
-		if (*s <= 0xef)
+		if (first_byte <= 0xef)
 			return 3;
 		return 4;
 	}
 
-	int next_codepoint(const unsigned char** str)
+	int next_codepoint(const unsigned char** str) override
 	{
 		int code;
 		const unsigned char *s = *str;
@@ -179,12 +179,12 @@ public:
 		return code;
 	}
 
-	char* fromUtf8(const char* s)
+	char* fromUtf8(const char* s) override
 	{
 		return strdup(s);
 	}
 
-	char* toUtf8(const char* s)
+	char* toUtf8(const char* s) override
 	{
 		return strdup(s);
 	}
@@ -194,7 +194,7 @@ int Encoding::mbslen(const unsigned char* s)
 {
 	int len = 0;
 	while (*s) {
-		s += mblen(s);
+		s += mblen(*s);
 		len++;
 	}
 	return len;
diff --git a/src/encoding.h b/src/encoding.h
index 83bf9e1..5b3cbf7 100644
--- a/src/encoding.h
+++ b/src/encoding.h
@@ -19,11 +19,8 @@ class Encoding {
 	int next_codepoint(const char** s) {
 		return next_codepoint(reinterpret_cast<const unsigned char **>(s));
 	}
-	// Returns byte length of the first character of s.
-	virtual int mblen(const unsigned char* s) = 0;
-	int mblen(const char* s) {
-		return mblen(reinterpret_cast<const unsigned char*>(s));
-	}
+	// Determines the byte length of a character based on the first byte.
+	virtual int mblen(unsigned char first_byte) = 0;
 	// Returns the number of characters in s.
 	int mbslen(const unsigned char* s);
 	int mbslen(const char* s) {
diff --git a/src/sys/nact.cpp b/src/sys/nact.cpp
index 708feed..7922eed 100644
--- a/src/sys/nact.cpp
+++ b/src/sys/nact.cpp
@@ -299,7 +299,7 @@ void NACT::message(uint8 terminator)
 		const uint8* begin = sco.ptr();
 		const uint8* p = begin;
 		while (is_message(*p))
-			p += encoding->mblen(p);
+			p += encoding->mblen(*p);
 		int len = p - begin;
 		sco.skip(len);
 
diff --git a/src/sys/nact_sys1.cpp b/src/sys/nact_sys1.cpp
index fb7ded3..e12e06a 100644
--- a/src/sys/nact_sys1.cpp
+++ b/src/sys/nact_sys1.cpp
@@ -218,8 +218,7 @@ void NACT_Sys1::cmd_branch()
 			} else if (cmd == '\'' || cmd == '"') {  // SysEng
 				sco.skip_syseng_string(encoding.get(), cmd);
 			} else if (is_message(cmd)) {
-				sco.ungetd();
-				sco.skip(encoding->mblen(sco.ptr()));
+				sco.skip(encoding->mblen(cmd) - 1);
 			} else {
 				sco.unknown_command(cmd);
 			}
diff --git a/src/sys/nact_sys2.cpp b/src/sys/nact_sys2.cpp
index d8815b5..79f8be0 100644
--- a/src/sys/nact_sys2.cpp
+++ b/src/sys/nact_sys2.cpp
@@ -251,8 +251,7 @@ void NACT_Sys2::cmd_branch()
 			} else if (cmd == '\'' || cmd == '"') {  // SysEng
 				sco.skip_syseng_string(encoding.get(), cmd);
 			} else if (is_message(cmd)) {
-				sco.ungetd();
-				sco.skip(encoding->mblen(sco.ptr()));
+				sco.skip(encoding->mblen(cmd) - 1);
 			} else {
 				sco.unknown_command(cmd);
 			}
diff --git a/src/sys/scenario.cpp b/src/sys/scenario.cpp
index c2176cb..f91eb3b 100644
--- a/src/sys/scenario.cpp
+++ b/src/sys/scenario.cpp
@@ -19,9 +19,9 @@ uint8_t Scenario::fetch_command()
 void Scenario::skip_syseng_string(Encoding *enc, uint8_t terminator)
 {
 	for (uint8_t c = getd(); c != terminator; c = getd()) {
-		if (c != '\\')
-			ungetd();
-		skip(enc->mblen(ptr()));
+		if (c == '\\')
+			c = getd();
+		skip(enc->mblen(c) - 1);
 	}
 }
 
@@ -29,14 +29,14 @@ void Scenario::get_syseng_string(char* buf, int size, Encoding *enc, uint8_t ter
 {
 	int i = 0;
 	for (uint8_t c = getd(); c != terminator; c = getd()) {
-		if (c != '\\')
-			ungetd();
-		int len = enc->mblen(ptr());
+		if (c == '\\')
+			c = getd();
+		int len = enc->mblen(c);
 		if (i + len >= size)
 			sys_error("String buffer overrun at %d:%04x", page_, cmd_addr_);
-		memcpy(&buf[i], ptr(), len);
-		i += len;
-		skip(len);
+		buf[i++] = c;
+		for (int j = 1; j < len; ++j)
+			buf[i++] = getd();
 	}
 	buf[i] = '\0';
 }