diff --git a/src/fileio.cpp b/src/fileio.cpp
index f82bbb4..5959611 100644
--- a/src/fileio.cpp
+++ b/src/fileio.cpp
@@ -27,15 +27,12 @@ int FILEIO::StatSavedata(const char* filename, struct stat* buf)
 	return stat(path, buf);
 }
 
-FILEIO::FILEIO()
+FILEIO::FILEIO() : fp(NULL), mode_(0)
 {
-	// 初期化
-	fp = NULL;
 }
 
 FILEIO::~FILEIO(void)
 {
-	// 後始末
 	if(fp != NULL) {
 		Fclose();
 	}
@@ -95,12 +92,12 @@ uint32 FILEIO::Ftell()
 	return ftell(fp);
 }
 
-uint32 FILEIO::Fread(void* buffer, uint32 size, uint32 count)
+size_t FILEIO::Fread(void* buffer, uint32 size, uint32 count)
 {
 	return fread(buffer, size, count, fp);
 }
 
-uint32 FILEIO::Fwrite(void* buffer, uint32 size, uint32 count)
+size_t FILEIO::Fwrite(void* buffer, uint32 size, uint32 count)
 {
 	return fwrite(buffer, size, count, fp);
 }
diff --git a/src/fileio.h b/src/fileio.h
index aedd4a9..0e2e80a 100644
--- a/src/fileio.h
+++ b/src/fileio.h
@@ -34,8 +34,8 @@ public:
 	void Fclose();
 	uint32 Fseek(long offset, int origin);
 	uint32 Ftell();
-	uint32 Fread(void* buffer, uint32 size, uint32 count);
-	uint32 Fwrite(void* buffer, uint32 size, uint32 count);
+	size_t Fread(void* buffer, uint32 size, uint32 count);
+	size_t Fwrite(void* buffer, uint32 size, uint32 count);
 	int Fgetc();
 	int Fgetw();
 	void Fgets(char* dest, int length);
diff --git a/src/fm/makofm.cpp b/src/fm/makofm.cpp
index c6174c5..aee3708 100644
--- a/src/fm/makofm.cpp
+++ b/src/fm/makofm.cpp
@@ -130,7 +130,7 @@ void MakoFM::ExecSequence(int ch, bool execcmd) {
 
  execcmd:
 	cmdFF = 0;
-	work[ch].seq_ptr = ExecCmd(ch, data + work[ch].seq_ptr) - data;
+	work[ch].seq_ptr = static_cast<uint16_t>(ExecCmd(ch, data + work[ch].seq_ptr) - data);
 	if (cmdFF) {
 		uint16_t block_addr = GetWord(work[ch].jump_ptr);
 		work[ch].jump_ptr += 2;
diff --git a/src/fm/makofm.h b/src/fm/makofm.h
index b97d0cd..d5f4fc9 100644
--- a/src/fm/makofm.h
+++ b/src/fm/makofm.h
@@ -16,7 +16,7 @@ public:
 	~MakoFM();
 	void MainLoop();
 
-	float GetTime() const { return time_ms; }
+	double GetTime() const { return time_ms; }
 	bool Looped() const { return part_looped == (1 << MAKO_MAXCH) - 1; }
 
 protected:
@@ -128,7 +128,7 @@ private:
 	uint8_t cmdFF;
 
 	unsigned part_looped = 0;
-	float time_ms = 0;
+	double time_ms = 0;
 	uint8_t current_mark;
 };
 
diff --git a/src/sys/ags_text.cpp b/src/sys/ags_text.cpp
index 7de2a53..4a4bd15 100644
--- a/src/sys/ags_text.cpp
+++ b/src/sys/ags_text.cpp
@@ -54,7 +54,7 @@ void AGS::draw_text(const char* string, bool text_wait)
 		// 文字コード取得
 		uint8 c = (uint8)string[p++];
 		uint16 code = c;
-		if(is_2byte_message(code)) {
+		if(is_2byte_message(c)) {
 			code = (code << 8) | (uint8)string[p++];
 		}
 		if(draw_hankaku) {
diff --git a/src/sys/mako_midi.cpp b/src/sys/mako_midi.cpp
index 76d519e..1503891 100644
--- a/src/sys/mako_midi.cpp
+++ b/src/sys/mako_midi.cpp
@@ -44,8 +44,8 @@ const uint8 smf_header[] = {
 };
 const size_t TRACK_LENGTH_OFFSET = 18;
 
-const size_t FADEOUT_DURATION = 100;  // 1 second
-const size_t MINIMUM_MUSIC_DURATION = 6000;  // 60 seconds
+const int FADEOUT_DURATION = 100;  // 1 second
+const int MINIMUM_MUSIC_DURATION = 6000;  // 60 seconds
 
 class SmfWriter {
 public:
@@ -64,7 +64,7 @@ public:
 		buf.push_back(0x00);
 
 		size_t length = buf.size() - (TRACK_LENGTH_OFFSET + 4);
-		buf[TRACK_LENGTH_OFFSET] = length >> 24;
+		buf[TRACK_LENGTH_OFFSET] = length >> 24 & 0xff;
 		buf[TRACK_LENGTH_OFFSET + 1] = length >> 16 & 0xff;
 		buf[TRACK_LENGTH_OFFSET + 2] = length >> 8 & 0xff;
 		buf[TRACK_LENGTH_OFFSET + 3] = length & 0xff;
@@ -133,7 +133,7 @@ private:
 		dt = 0;
 	}
 
-	uint8 fade(uint8 level) {
+	int fade(int level) {
 		if (fadeout_start < 0)
 			return level;
 		return level * (fadeout_start + FADEOUT_DURATION - total_ticks) / FADEOUT_DURATION;
@@ -565,10 +565,7 @@ void MAKOMidi::load_mda(int page)
 	// MDAデータの読み込み
 	char path[16];
 	strcpy_s(path, 16, amus);
-	int p = strlen(path);
-	path[p - 3] = 'M';
-	path[p - 2] = 'D';
-	path[p - 1] = 'A';
+	strcpy(path + strlen(path) - 3, "MDA");
 
 	DRI* dri = new DRI();
 	int size;
diff --git a/src/sys/nact.cpp b/src/sys/nact.cpp
index 62b07d2..bbf7b48 100644
--- a/src/sys/nact.cpp
+++ b/src/sys/nact.cpp
@@ -302,7 +302,7 @@ void NACT::message()
 		else
 			break;
 	}
-	int len = end - begin;
+	int len = static_cast<int>(end - begin);
 	scenario_addr += len;
 
 	char* buf = (char*)alloca(len + 1);
diff --git a/src/sys/nact_input.cpp b/src/sys/nact_input.cpp
index ed874b7..67fc89f 100644
--- a/src/sys/nact_input.cpp
+++ b/src/sys/nact_input.cpp
@@ -35,8 +35,8 @@ void NACT::pump_events()
 		case SDL_FINGERDOWN:
 		case SDL_FINGERUP:
 		case SDL_FINGERMOTION:
-			mousex = e.tfinger.x * 640;
-			mousey = e.tfinger.y * ags->screen_height;
+			mousex = static_cast<int>(e.tfinger.x) * 640;
+			mousey = static_cast<int>(e.tfinger.y) * ags->screen_height;
 			fingers = SDL_GetNumTouchFingers(e.tfinger.touchId);
 			break;
 
diff --git a/src/win/mako.cpp b/src/win/mako.cpp
index 9320b8d..597f26c 100644
--- a/src/win/mako.cpp
+++ b/src/win/mako.cpp
@@ -318,7 +318,7 @@ void MAKO::play_music(int page)
 
 	stop_music();
 
-	int track = page < 100 ? cd_track[page] : 0;
+	size_t track = page < 100 ? cd_track[page] : 0;
 	if (track) {
 		if (track >= playlist.size() || !playlist[track])
 			return;