diff --git a/src/sys/ags.cpp b/src/sys/ags.cpp
index d29d7e3..0661097 100644
--- a/src/sys/ags.cpp
+++ b/src/sys/ags.cpp
@@ -330,10 +330,6 @@ AGS::AGS(NACT* parent, const Config& config) : nact(parent), dirty(false)
 	// マウスカーソル
 	cursor_color = 15;
 	cursor_index = 0;
-
-	// フェード状態
-	fader = false;
-	memset(fader_screen, 0, sizeof(fader_screen));
 }
 
 AGS::~AGS()
@@ -405,51 +401,36 @@ void AGS::set_pixel(int dest, int x, int y, uint8 color)
 	vram[dest][y][x] = color;
 }
 
-void AGS::fade_start()
+void AGS::fade_out(int duration_ms, bool white)
 {
-	memcpy(fader_screen, hBmpDest->pixels, sizeof(fader_screen));
-}
+	if (fade_level)
+		return;
 
-void AGS::fade_end()
-{
-	memcpy(hBmpDest->pixels, fader_screen, sizeof(fader_screen));
-}
+	fade_color = white ? 255 : 0;
 
-void AGS::fade_out(int depth, bool white)
-{
-	// 通常画面 → 白黒画面
-	int fx = fade_x[depth];
-	int fy = fade_y[depth];
-	fader = true;
-
-	for(int y = 0; y < 480; y += 4) {
-		uint32* dest = surface_line(hBmpDest, y + fy) + fx;
-		for(int x = 0; x < 640; x += 4) {
-			dest[x] = white ? 0xffffff : 0;
-		}
+	Uint32 dwStart = SDL_GetTicks();
+	while (fade_level < 255) {
+		nact->sys_sleep(16);
+		int t = SDL_GetTicks() - dwStart;
+		fade_level = t >= duration_ms ? 255 : t * 255 / duration_ms;
+		dirty = true;
 	}
-
-	// 画面更新
-	invalidate_screen(0, 0, 640, screen_height);
+	update_screen();
 }
 
-void AGS::fade_in(int depth)
+void AGS::fade_in(int duration_ms)
 {
-	// 白黒画面 → 通常画面
-	int fx = fade_x[depth];
-	int fy = fade_y[depth];
-	fader = (depth == 15) ? false : true;
+	if (fade_level == 0)
+		return;
 
-	for(int y = 0; y < 480; y += 4) {
-		uint32* src = &fader_screen[640 * (y + fy) + fx];
-		uint32* dest = surface_line(hBmpDest, y + fy) + fx;
-		for(int x = 0; x < 640; x += 4) {
-			dest[x] = src[x];
-		}
+	Uint32 dwStart = SDL_GetTicks();
+	while (fade_level > 0) {
+		nact->sys_sleep(16);
+		int t = SDL_GetTicks() - dwStart;
+		fade_level = t >= duration_ms ? 0 : (duration_ms - t) * 255 / duration_ms;
+		dirty = true;
 	}
-
-	// 画面更新
-	invalidate_screen(0, 0, 640, screen_height);
+	update_screen();
 }
 
 void AGS::flush_screen(bool update)
@@ -473,36 +454,20 @@ void AGS::flush_screen(bool update)
 
 void AGS::draw_screen(int sx, int sy, int width, int height)
 {
-	if(fader) {
-		for(int y = sy; y < (sy + height) && y < 480; y++) {
-			uint32* src = vram[0][y];
-			uint32* dest = &fader_screen[640 * y];
-			for(int x = sx; x < (sx + width) && x < 640; x++) {
-				uint32 a=src[x];
-				if (nact->sys_ver == 3 && src[x] & 0x80000000) {
-					// あゆみちゃん物語 フルカラー実写版
-					dest[x] = src[x] & 0xffffff;
-				} else {
-					dest[x] = screen_palette[src[x] & 0xff];
-				}
+	for(int y = sy; y < (sy + height) && y < 480; y++) {
+		uint32* src = vram[0][y];
+		uint32* dest = surface_line(hBmpDest, y);
+		for(int x = sx; x < (sx + width) && x < 640; x++) {
+			uint32 a=src[x];
+			if (nact->sys_ver == 3 && src[x] & 0x80000000) {
+				// あゆみちゃん物語 フルカラー実写版
+				dest[x] = src[x] & 0xffffff;
+			} else {
+				dest[x] = screen_palette[src[x] & 0xff];
 			}
 		}
-	} else {
-		for(int y = sy; y < (sy + height) && y < 480; y++) {
-			uint32* src = vram[0][y];
-			uint32* dest = surface_line(hBmpDest, y);
-			for(int x = sx; x < (sx + width) && x < 640; x++) {
-				uint32 a=src[x];
-				if (nact->sys_ver == 3 && src[x] & 0x80000000) {
-					// あゆみちゃん物語 フルカラー実写版
-					dest[x] = src[x] & 0xffffff;
-				} else {
-					dest[x] = screen_palette[src[x] & 0xff];
-				}
-			}
-		}
-		invalidate_screen(sx, sy, width, height);
 	}
+	invalidate_screen(sx, sy, width, height);
 }
 
 void AGS::invalidate_screen(int sx, int sy, int width, int height)
@@ -528,6 +493,12 @@ void AGS::update_screen()
 		return;
 	SDL_RenderClear(sdlRenderer);
 	SDL_RenderCopy(sdlRenderer, sdlTexture, NULL, NULL);
+	if (fade_level) {
+		SDL_SetRenderDrawBlendMode(sdlRenderer, SDL_BLENDMODE_BLEND);
+		SDL_SetRenderDrawColor(sdlRenderer, fade_color, fade_color, fade_color, fade_level);
+		SDL_RenderFillRect(sdlRenderer, NULL);
+		SDL_SetRenderDrawBlendMode(sdlRenderer, SDL_BLENDMODE_NONE);
+	}
 	SDL_RenderPresent(sdlRenderer);
 	dirty = false;
 }
diff --git a/src/sys/ags.h b/src/sys/ags.h
index 72d35fa..982e5f1 100644
--- a/src/sys/ags.h
+++ b/src/sys/ags.h
@@ -12,10 +12,6 @@
 #include "nact.h"
 #include <SDL_ttf.h>
 
-// フェード処理
-static const int fade_x[16] = {0, 2, 2, 0, 1, 3, 3, 1, 1, 3, 3, 1, 0, 2, 2, 0};
-static const int fade_y[16] = {0, 2, 0, 2, 1, 3, 1, 3, 0, 2, 0, 2, 1, 3, 1, 3};
-
 #define MAX_CG 10000
 
 static inline uint32 SETPALETTE256(uint32 R, uint32 G, uint32 B)
@@ -89,8 +85,8 @@ private:
 	uint32 screen_palette[256];
 	uint8 gaiji[188][32];
 
-	bool fader;	// フェードの状態
-	uint32 fader_screen[640 * 480];
+	int fade_level = 0;  // 0-255
+	int fade_color = 0;  // 0: black, 255: white
 
 public:
 	AGS(NACT* parent, const Config& config);
@@ -106,11 +102,8 @@ public:
 	uint8 get_pixel(int dest, int x, int y);
 	void set_pixel(int dest, int x, int y, uint8 color);
 
-	void fade_start();
-	void fade_end();
-	void fade_out(int depth, bool white);
-	void fade_in(int depth);
-	bool now_fade() { return fader; }
+	void fade_out(int duration_ms, bool white);
+	void fade_in(int duration_ms);
 
 	void copy(int sx, int sy, int ex, int ey, int dx, int dy);
 	void gcopy(int gsc, int gde, int glx, int gly, int gsw);
diff --git a/src/sys/ags_window.cpp b/src/sys/ags_window.cpp
index 6741ebe..66158a4 100644
--- a/src/sys/ags_window.cpp
+++ b/src/sys/ags_window.cpp
@@ -15,7 +15,7 @@ void AGS::clear_text_window(int index, bool erase)
 	int ey = text_w[index - 1].ey;
 
 	if(erase) {
-		if(text_w[index - 1].frame && fader) {
+		if(text_w[index - 1].frame && fade_level) {
 			draw_window(sx - 8, sy - 8, ex + 8, ey + 8, true, text_frame_color, text_back_color);
 		} else {
 			box_fill(0, sx, sy, ex, ey, text_back_color);
@@ -95,7 +95,7 @@ void AGS::open_text_window(int index, bool erase)
 		text_w[index - 1].screen_height = height;
 
 		for(int y = 0; y < height && y + sy < 480; y++) {
-			uint32* scr = fader ? &fader_screen[640 * (y + sy) + sx] : surface_line(hBmpDest, y + sy) + sx;
+			uint32* scr = surface_line(hBmpDest, y + sy) + sx;
 			for(int x = 0; x < width && x + sx < 640; x++) {
 				uint32 col = vram[0][y + sy][x + sx];
 				if(!(col & 0x80000000)) {
@@ -157,7 +157,7 @@ void AGS::close_text_window(int index, bool update)
 		text_w[index - 1].window_height = height;
 
 		for(int y = 0; y < height && y + sy < 480; y++) {
-			uint32* scr = fader ? &fader_screen[640 * (y + sy) + sx] : surface_line(hBmpDest, y + sy) + sx;
+			uint32* scr = surface_line(hBmpDest, y + sy) + sx;
 			for(int x = 0; x < width && x + sx < 640; x++) {
 				uint32 col = vram[0][y + sy][x + sx];
 				if(!(col & 0x80000000)) {
@@ -230,7 +230,7 @@ void AGS::open_menu_window(int index)
 		menu_w[index - 1].screen_height = wheight;
 
 		for(int y = 0; y < wheight && y + wsy < 480; y++) {
-			uint32* scr = fader ? &fader_screen[640 * (y + wsy) + wsx] : surface_line(hBmpDest, y + wsy) + wsx;
+			uint32* scr = surface_line(hBmpDest, y + wsy) + wsx;
 			for(int x = 0; x < wwidth && x + wsx < 640; x++) {
 				uint32 col = vram[0][y + wsy][x + wsx];
 				if(!(col & 0x80000000)) {
diff --git a/src/sys/nact.h b/src/sys/nact.h
index f8693be..16c84af 100644
--- a/src/sys/nact.h
+++ b/src/sys/nact.h
@@ -227,7 +227,6 @@ protected:
 	int menu_select(int num_items);
 	void wait_after_open_menu();
 
-	void sys_sleep(int ms);
 	uint8 get_key();
 	void get_cursor(int* x, int* y);
 	void set_cursor(int x, int y);
@@ -253,6 +252,7 @@ protected:
 
 public:
 	bool mainloop();
+	void sys_sleep(int ms);
 
 	int get_screen_height();
 
diff --git a/src/sys/nact_sys2.cpp b/src/sys/nact_sys2.cpp
index cb818d2..f9aee42 100644
--- a/src/sys/nact_sys2.cpp
+++ b/src/sys/nact_sys2.cpp
@@ -1188,29 +1188,11 @@ void NACT_Sys2::cmd_y()
 			break;
 		case 40:
 		case 42:
-			if(ags->now_fade()) {
-				Uint32 dwStart = SDL_GetTicks();
-				for(int i = 0; i < 16; i++) {
-					ags->fade_in(i);
-					int32 ms = dwStart + param * 1000 / 60 * i - SDL_GetTicks();
-					if (ms > 0)
-						sys_sleep(ms);
-				}
-				ags->fade_end();
-			}
+			ags->fade_in(param * 16 * 1000 / 60);
 			break;
 		case 41:
 		case 43:
-			if(!ags->now_fade()) {
-				ags->fade_start();
-				Uint32 dwStart = SDL_GetTicks();
-				for(int i = 0; i < 16; i++) {
-					ags->fade_out(i, (cmd == 41) ? false : true);
-					int32 ms = dwStart + param * 1000 / 60 * i - SDL_GetTicks();
-					if (ms > 0)
-						sys_sleep(ms);
-				}
-			}
+			ags->fade_out(param * 16 * 1000 / 60, cmd == 43);
 			break;
 		case 221:
 		case 222:
diff --git a/src/sys/nact_sys3.cpp b/src/sys/nact_sys3.cpp
index 3dd5173..e554f9a 100644
--- a/src/sys/nact_sys3.cpp
+++ b/src/sys/nact_sys3.cpp
@@ -1160,29 +1160,11 @@ void NACT_Sys3::cmd_y()
 			break;
 		case 40:
 		case 42:
-			if(ags->now_fade()) {
-				Uint32 dwStart = SDL_GetTicks();
-				for(int i = 0; i < 16; i++) {
-					ags->fade_in(i);
-					int32 ms = dwStart + param * 1000 / 60 * i - SDL_GetTicks();
-					if (ms > 0)
-						sys_sleep(ms);
-				}
-				ags->fade_end();
-			}
+			ags->fade_in(param * 16 * 1000 / 60);
 			break;
 		case 41:
 		case 43:
-			if(!ags->now_fade()) {
-				ags->fade_start();
-				Uint32 dwStart = SDL_GetTicks();
-				for(int i = 0; i < 16; i++) {
-					ags->fade_out(i, (cmd == 41) ? false : true);
-					int32 ms = dwStart + param * 1000 / 60 * i - SDL_GetTicks();
-					if (ms > 0)
-						sys_sleep(ms);
-				}
-			}
+			ags->fade_out(param * 16 * 1000 / 60, cmd == 43);
 			break;
 		case 45:
 			ags->extract_palette = param ? true : false;