diff --git a/src/sys/ags.h b/src/sys/ags.h
index 5d6a92c..640ffe0 100644
--- a/src/sys/ags.h
+++ b/src/sys/ags.h
@@ -129,7 +129,6 @@ public:
 					 int transparent_color = -1);
 	void gcopy(int gsc, int gde, int glx, int gly, int gsw);
 	void paint(int x, int y, uint8 color);
-	void draw_box(int index);
 	void draw_mesh(int sx, int sy, int width, int height);
 	void box_fill(int dest, int sx, int sy, int ex, int ey, uint8 color);
 	void box_line(int dest, int sx, int sy, int ex, int ey, uint8 color);
@@ -162,10 +161,6 @@ public:
 		menu_w[index - 1].frame = frame;
 	}
 
-	void set_box(int index, uint8 color, int sx, int sy, int ex, int ey) {
-		box[index - 1] = {color, sx, sy, ex, ey};
-	}
-
 	void load_cursor(int page);
 	void select_cursor();
 	void translate_mouse_coords(int* x, int* y);
@@ -248,16 +243,6 @@ public:
 private:
 	void init_windows();
 
-	// Box (E and Y7 commands)
-	struct Box {
-		uint8 color = 0;
-		int sx = 0;
-		int sy = 0;
-		int ex = 639;
-		int ey = 399;
-	};
-	Box box[20];
-
 	Dri acg;
 	const char* bmp_prefix = NULL;
 	const uint8_t* push_bitmap = nullptr;
diff --git a/src/sys/ags_draw.cpp b/src/sys/ags_draw.cpp
index 84c1eaf..8626459 100644
--- a/src/sys/ags_draw.cpp
+++ b/src/sys/ags_draw.cpp
@@ -216,22 +216,6 @@ void AGS::paint(int x, int y, uint8 color)
 	invalidate_screen(minx, miny, maxx - minx + 1, maxy - miny + 1);
 }
 
-void AGS::draw_box(int index)
-{
-	if(index == 0) {
-		// 全画面消去
-		box_fill(dest_screen, 0, 0, 639, 479, 0);
-		return;
-	}
-
-	Box& b = box[index - 1];
-	if (1 <= index && index <= 10) {
-		box_fill(dest_screen, b.sx, b.sy, b.ex, b.ey, b.color);
-	} else if (11 <= index && index <= 20) {
-		box_line(dest_screen, b.sx, b.sy, b.ex, b.ey, b.color);
-	}
-}
-
 void AGS::draw_mesh(int sx, int sy, int width, int height)
 {
 	// super d.p.s
diff --git a/src/sys/nact.h b/src/sys/nact.h
index a2bf869..59ba0bf 100644
--- a/src/sys/nact.h
+++ b/src/sys/nact.h
@@ -122,6 +122,17 @@ protected:
 	bool show_push = true;		// Push表示
 	bool clear_text = true;	// メニュー後のメッセージウィンドウ消去
 
+	// Box (E and Y7 commands)
+	struct Box {
+		uint8 color = 0;
+		int sx = 0;
+		int sy = 0;
+		int ex = 639;
+		int ey = 399;
+	};
+	Box box[20];
+	void draw_box(int index);
+
 	struct MenuItem {
 		uint16_t addr;
 		uint8_t verb;
diff --git a/src/sys/nact_gakuenking.cpp b/src/sys/nact_gakuenking.cpp
index aec2b2a..c160a1a 100644
--- a/src/sys/nact_gakuenking.cpp
+++ b/src/sys/nact_gakuenking.cpp
@@ -42,8 +42,8 @@ public:
 	NACT_GakuenKing(const Config& config, const GameId& game_id)
 		: NACT_Sys3(config, game_id) {
 		text_wait_time = 0;	// Y 13 and Y 14 set this
-		ags->set_box(1, 0, 16, 8, 367, 295);
-		ags->set_box(2, 0, 40, 0, 599, 298);
+		box[0] = {0, 16, 8, 367, 295};
+		box[1] = {0, 40, 0, 599, 298};
 		load_executable_data();
 		amap.open("AMAP.DAT");
 		map_base.fill(0);
diff --git a/src/sys/nact_sys1.cpp b/src/sys/nact_sys1.cpp
index 0a4e13b..1910745 100644
--- a/src/sys/nact_sys1.cpp
+++ b/src/sys/nact_sys1.cpp
@@ -547,7 +547,7 @@ public:
 		WAIT(2000);
 		ags->load_cg(38, -1);
 		cmd_a();
-		ags->draw_box(0);
+		draw_box(0);
 	}
 };
 
@@ -883,7 +883,7 @@ public:
 			ags->load_cg(180, -1);
 
 			WAIT(2000);
-			ags->draw_box(0);
+			draw_box(0);
 			ags->dest_screen = 1;
 			ags->load_cg(173, -1);
 			ags->dest_screen = 0;
@@ -902,7 +902,7 @@ public:
 				ags->gcopy(i + 0x2306, i + 0x2306, 1, 165, 3);
 			}
 			WAIT_KEYQUIT(6000);
-			ags->draw_box(param);
+			draw_box(param);
 			break;
 		default:
 			exec_y(cmd, param);
diff --git a/src/sys/nact_sys2.cpp b/src/sys/nact_sys2.cpp
index 8fe7325..3814a15 100644
--- a/src/sys/nact_sys2.cpp
+++ b/src/sys/nact_sys2.cpp
@@ -86,18 +86,18 @@ NACT_Sys2::NACT_Sys2(const Config& config, const GameId& game_id)
 	: NACT(config, game_id)
 {
 	if (game_id.is(GameId::SDPS_TONO) || game_id.is(GameId::SDPS_KAIZOKU)) {
-		ags->set_box(1, 0, 40, 8, 598, 271);
+		box[0] = {0, 40, 8, 598, 271};
 	} else if (game_id.is(GameId::PROG_FD)) {
-		ags->set_box(1, 0, 64, 13, 407, 289);
-		ags->set_box(2, 0, 24, 298, 111, 390);
-		ags->set_box(3, 0, 0, 0, 639, 307);
-		ags->set_box(4, 0, 0, 0, 319, 399);
-		ags->set_box(5, 0, (16*8), 310, ((77*8)-1), 390);
-		ags->set_box(6, 0, (4*8), 310, ((76*8)-1), 390);
-		ags->set_box(7, 0, (2*8), 317, ((56*8)-1), 389);
-		ags->set_box(8, 15, 64, 13, 407, 289);
-		ags->set_box(9, 0, 0, 0, 319, 399);
-		ags->set_box(10, 0, 320, 0, 639, 40);
+		box[0] = {0, 64, 13, 407, 289};
+		box[1] = {0, 24, 298, 111, 390};
+		box[2] = {0, 0, 0, 639, 307};
+		box[3] = {0, 0, 0, 319, 399};
+		box[4] = {0, (16*8), 310, ((77*8)-1), 390};
+		box[5] = {0, (4*8), 310, ((76*8)-1), 390};
+		box[6] = {0, (2*8), 317, ((56*8)-1), 389};
+		box[7] = {15, 64, 13, 407, 289};
+		box[8] = {0, 0, 0, 319, 399};
+		box[9] = {0, 320, 0, 639, 40};
 	}
 }
 
@@ -733,7 +733,7 @@ void NACT_Sys2::cmd_y()
 			break;
 		case 7:
 			if (!game_id.is(GameId::SDPS_MARIA)) {
-				ags->draw_box(param);
+				draw_box(param);
 			}
 			break;
 		case 8:
diff --git a/src/sys/nact_sys3.cpp b/src/sys/nact_sys3.cpp
index 667a8ad..e7408cc 100644
--- a/src/sys/nact_sys3.cpp
+++ b/src/sys/nact_sys3.cpp
@@ -241,7 +241,7 @@ void NACT_Sys3::cmd_e()
 		sx = sx * 8;
 		ex = ex * 8 - 1;
 	}
-	ags->set_box(index, color, sx, sy, ex, ey);
+	box[index - 1] = {color, sx, sy, ex, ey};
 }
 
 void NACT_Sys3::cmd_g()
@@ -720,7 +720,7 @@ void NACT_Sys3::exec_y(int cmd, int param)
 		case 6:
 			break;
 		case 7:
-			ags->draw_box(param);
+			draw_box(param);
 			break;
 		case 8:
 			tvar_index = param;
diff --git a/src/sys/nact_window.cpp b/src/sys/nact_window.cpp
index e7559e6..3898cdd 100644
--- a/src/sys/nact_window.cpp
+++ b/src/sys/nact_window.cpp
@@ -78,3 +78,19 @@ void NACT::save_display_state(FILEIO* fio)
 		fio->putw(0);
 	}
 }
+
+void NACT::draw_box(int index)
+{
+	if (index == 0) {
+		// Clear the entire screen
+		ags->box_fill(ags->dest_screen, 0, 0, 639, 479, 0);
+		return;
+	}
+
+	Box& b = box[index - 1];
+	if (1 <= index && index <= 10) {
+		ags->box_fill(ags->dest_screen, b.sx, b.sy, b.ex, b.ey, b.color);
+	} else if (11 <= index && index <= 20) {
+		ags->box_line(ags->dest_screen, b.sx, b.sy, b.ex, b.ey, b.color);
+	}
+}