diff --git a/include/reign.h b/include/reign.h
index a454b17..c7cdb86 100644
--- a/include/reign.h
+++ b/include/reign.h
@@ -18,9 +18,11 @@
 #define SYSTEM4_REIGN_H
 
 #define RE_MAX_INSTANCES 32
+#define RE_NR_BACK_CGS 16
 
 #include <cglm/types.h>
 
+#include "gfx/gfx.h"
 #include "plugin.h"
 
 enum RE_motion_state {
@@ -40,6 +42,17 @@ struct RE_camera {
 	float pitch, roll, yaw;  // in degrees
 };
 
+struct RE_back_cg {
+	struct texture texture;
+	struct string *name;
+	int no;
+	float blend_rate;
+	float x;
+	float y;
+	float mag;
+	bool show;
+};
+
 struct RE_plugin {
 	struct draw_plugin plugin;
 	int sprite;
@@ -49,6 +62,8 @@ struct RE_plugin {
 	struct RE_camera camera;
 	mat4 proj_transform;
 
+	struct RE_back_cg back_cg[RE_NR_BACK_CGS];
+
 	// Settings.
 	int render_mode;
 	int shadow_mode;
@@ -116,6 +131,9 @@ bool RE_motion_set_frame(struct motion *motion, float frame);
 bool RE_motion_set_frame_range(struct motion *motion, float begin, float end);
 bool RE_motion_set_loop_frame_range(struct motion *motion, float begin, float end);
 
+bool RE_back_cg_set(struct RE_back_cg *bcg, int no);
+bool RE_back_cg_set_name(struct RE_back_cg *bcg, struct string *name, struct archive *aar);
+
 void RE_render(struct sact_sprite *sp);
 void RE_debug_print(struct sact_sprite *sp, int indent);
 
diff --git a/src/3d/debug.c b/src/3d/debug.c
new file mode 100644
index 0000000..5c636c7
--- /dev/null
+++ b/src/3d/debug.c
@@ -0,0 +1,96 @@
+/* Copyright (C) 2022 kichikuou <KichikuouChrome@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://gnu.org/licenses/>.
+ */
+
+#include "system4/string.h"
+
+#include "3d_internal.h"
+#include "reign.h"
+#include "sprite.h"
+#include "xsystem4.h"
+
+static void print_motion(const char *name, struct motion *m, int indent)
+{
+	const char *state;
+	switch (m->state) {
+	case RE_MOTION_STATE_STOP: state = "STOP"; break;
+	case RE_MOTION_STATE_NOLOOP: state = "NOLOOP"; break;
+	case RE_MOTION_STATE_LOOP: state = "LOOP"; break;
+	default: state = "?"; break;
+	}
+	indent_printf(indent, "%s = {name=\"%s\", state=%s, frame=%f},\n",
+	              name, m->name, state, m->current_frame);
+}
+
+static void print_instance(struct RE_instance *inst, int index, int indent)
+{
+	if (!inst || !inst->model)
+		return;
+	indent_printf(indent, "instance[%d] = {\n", index);
+	indent++;
+
+	indent_printf(indent, "path = \"%s\",\n", inst->model->path);
+	indent_printf(indent, "type = %d,\n", inst->type);
+	indent_printf(indent, "draw = %d,\n", inst->draw);
+	indent_printf(indent, "pos = {x=%f, y=%f, z=%f},\n", inst->pos[0], inst->pos[1], inst->pos[2]);
+	indent_printf(indent, "vec = {x=%f, y=%f, z=%f},\n", inst->vec[0], inst->vec[1], inst->vec[2]);
+	indent_printf(indent, "scale = {x=%f, y=%f, z=%f},\n", inst->scale[0], inst->scale[1], inst->scale[2]);
+	if (inst->motion)
+		print_motion("motion", inst->motion, indent);
+	if (inst->next_motion)
+		print_motion("next_motion", inst->next_motion, indent);
+	indent_printf(indent, "fps = %f,\n", inst->fps);
+	if (inst->motion_blend)
+		indent_printf(indent, "motion_blend_rate = %f,\n", inst->motion_blend_rate);
+
+	indent--;
+	indent_printf(indent, "},\n");
+}
+
+static void print_back_cg(struct RE_back_cg *bcg, int index, int indent)
+{
+	if (!bcg->name && !bcg->no)
+		return;
+	indent_printf(indent, "backCG[%d] = {\n", index);
+	indent++;
+
+	if (bcg->no)
+		indent_printf(indent, "no = %d,\n", bcg->no);
+	if (bcg->name)
+		indent_printf(indent, "name = \"%s\",\n", bcg->name ? bcg->name->text : "");
+	indent_printf(indent, "pos = {x=%f, y=%f},\n", bcg->x, bcg->y);
+	indent_printf(indent, "blend_rate = %f,\n", bcg->blend_rate);
+	indent_printf(indent, "mag = %f,\n", bcg->mag);
+	indent_printf(indent, "show = %d,\n", bcg->show);
+
+	indent--;
+	indent_printf(indent, "},\n");
+}
+
+void RE_debug_print(struct sact_sprite *sp, int indent)
+{
+	struct RE_plugin *p = (struct RE_plugin *)sp->plugin;
+
+	indent_printf(indent, "name = \"%s\",\n", p->plugin.name);
+	indent_printf(indent, "camera = {x=%f, y=%f, z=%f, pitch=%f, roll=%f, yaw=%f},\n",
+	              p->camera.pos[0], p->camera.pos[1], p->camera.pos[2],
+	              p->camera.pitch, p->camera.roll, p->camera.yaw);
+
+	for (int i = 0; i < RE_MAX_INSTANCES; i++)
+		print_instance(p->instances[i], i, indent);
+
+	for (int i = 0; i < RE_NR_BACK_CGS; i++)
+		print_back_cg(&p->back_cg[i], i, indent);
+}
diff --git a/src/3d/reign.c b/src/3d/reign.c
index a9314ad..8e50930 100644
--- a/src/3d/reign.c
+++ b/src/3d/reign.c
@@ -22,8 +22,11 @@
 
 #include "system4.h"
 #include "system4/aar.h"
+#include "system4/cg.h"
+#include "system4/string.h"
 
 #include "3d_internal.h"
+#include "asset_manager.h"
 #include "reign.h"
 #include "sact.h"
 #include "xsystem4.h"
@@ -67,6 +70,19 @@ static void free_instance(struct RE_instance *instance)
 	free(instance);
 }
 
+static void RE_back_cg_init(struct RE_back_cg *bcg)
+{
+	bcg->blend_rate = 1.0;
+	bcg->mag = 1.0;
+}
+
+static void RE_back_cg_destroy(struct RE_back_cg *bcg)
+{
+	gfx_delete_texture(&bcg->texture);
+	if (bcg->name)
+		free_string(bcg->name);
+}
+
 struct RE_plugin *RE_plugin_new(void)
 {
 	char *aar_path = gamedir_path("Data/ReignData.red");
@@ -86,6 +102,8 @@ struct RE_plugin *RE_plugin_new(void)
 	plugin->plugin.update = RE_render;
 	plugin->plugin.debug_print = RE_debug_print;
 	plugin->aar = aar;
+	for (int i = 0; i < RE_NR_BACK_CGS; i++)
+		RE_back_cg_init(&plugin->back_cg[i]);
 	return plugin;
 }
 
@@ -98,6 +116,8 @@ void RE_plugin_free(struct RE_plugin *plugin)
 	archive_free(plugin->aar);
 	if (plugin->renderer)
 		RE_renderer_free(plugin->renderer);
+	for (int i = 0; i < RE_NR_BACK_CGS; i++)
+		RE_back_cg_destroy(&plugin->back_cg[i]);
 	free(plugin);
 }
 
@@ -240,50 +260,52 @@ bool RE_motion_set_loop_frame_range(struct motion *motion, float begin, float en
 	return true;
 }
 
-static void print_motion(const char *name, struct motion *m, int indent)
+bool RE_back_cg_set(struct RE_back_cg *bcg, int no)
 {
-	const char *state;
-	switch (m->state) {
-	case RE_MOTION_STATE_STOP: state = "STOP"; break;
-	case RE_MOTION_STATE_NOLOOP: state = "NOLOOP"; break;
-	case RE_MOTION_STATE_LOOP: state = "LOOP"; break;
-	default: state = "?"; break;
+	if (!bcg)
+		return false;
+	if (bcg->name) {
+		free_string(bcg->name);
+		bcg->name = NULL;
 	}
-	indent_printf(indent, "%s = {name=\"%s\", state=%s, frame=%f},\n",
-	              name, m->name, state, m->current_frame);
+	bcg->no = no;
+	gfx_delete_texture(&bcg->texture);
+
+	struct cg *cg = asset_cg_load(no);
+	if (!cg) {
+		WARNING("cannot load back CG: %d", no);
+		return false;
+	}
+	gfx_init_texture_with_cg(&bcg->texture, cg);
+	cg_free(cg);
+	return true;
 }
 
-void RE_debug_print(struct sact_sprite *sp, int indent)
+bool RE_back_cg_set_name(struct RE_back_cg *bcg, struct string *name, struct archive *aar)
 {
-	struct RE_plugin *p = (struct RE_plugin *)sp->plugin;
+	if (!bcg)
+		return false;
+	if (bcg->name)
+		free_string(bcg->name);
+	bcg->name = string_ref(name);
+	bcg->no = 0;
+	gfx_delete_texture(&bcg->texture);
 
-	indent_printf(indent, "name = \"%s\",\n", p->plugin.name);
-	indent_printf(indent, "camera = {x=%f, y=%f, z=%f, pitch=%f, roll=%f, yaw=%f},\n",
-	              p->camera.pos[0], p->camera.pos[1], p->camera.pos[2],
-	              p->camera.pitch, p->camera.roll, p->camera.yaw);
-
-	for (int i = 0; i < RE_MAX_INSTANCES; i++) {
-		struct RE_instance *inst = p->instances[i];
-		if (!inst || !inst->model)
-			continue;
-		indent_printf(indent, "instance[%d] = {\n", i);
-		indent++;
-
-		indent_printf(indent, "path = \"%s\",\n", inst->model->path);
-		indent_printf(indent, "type = %d,\n", inst->type);
-		indent_printf(indent, "draw = %d,\n", inst->draw);
-		indent_printf(indent, "pos = {x=%f, y=%f, z=%f},\n", inst->pos[0], inst->pos[1], inst->pos[2]);
-		indent_printf(indent, "vec = {x=%f, y=%f, z=%f},\n", inst->vec[0], inst->vec[1], inst->vec[2]);
-		indent_printf(indent, "scale = {x=%f, y=%f, z=%f},\n", inst->scale[0], inst->scale[1], inst->scale[2]);
-		if (inst->motion)
-			print_motion("motion", inst->motion, indent);
-		if (inst->next_motion)
-			print_motion("next_motion", inst->next_motion, indent);
-		indent_printf(indent, "fps = %f,\n", inst->fps);
-		if (inst->motion_blend)
-			indent_printf(indent, "motion_blend_rate = %f,\n", inst->motion_blend_rate);
-
-		indent--;
-		indent_printf(indent, "},\n");
+	char *cg_path = xmalloc(name->size + 5);
+	sprintf(cg_path, "%s.bmp", name->text);
+	struct archive_data *dfile = archive_get_by_name(aar, cg_path);
+	free(cg_path);
+	if (!dfile) {
+		WARNING("cannot load back CG %s", name->text);
+		return false;
 	}
+	struct cg *cg = cg_load_data(dfile);
+	archive_free_data(dfile);
+	if (!cg) {
+		WARNING("cg_load_data failed: %s", name->text);
+		return false;
+	}
+	gfx_init_texture_with_cg(&bcg->texture, cg);
+	cg_free(cg);
+	return true;
 }
diff --git a/src/3d/renderer.c b/src/3d/renderer.c
index 06468cf..98eb327 100644
--- a/src/3d/renderer.c
+++ b/src/3d/renderer.c
@@ -190,6 +190,15 @@ static void render_instance(struct RE_instance *inst, struct RE_renderer *r, mat
 	glUseProgram(0);
 }
 
+static void render_back_cg(struct texture *dst, struct RE_back_cg *bcg, struct RE_renderer *r)
+{
+	if (!bcg->texture.handle)
+		return;
+	int sw = bcg->texture.w;
+	int sh = bcg->texture.h;
+	gfx_copy_stretch_blend(dst, bcg->x, bcg->y, sw * bcg->mag, sh * bcg->mag, &bcg->texture, 0, 0, sw, sh, bcg->blend_rate * 255);
+}
+
 void RE_render(struct sact_sprite *sp)
 {
 	uint32_t timestamp = SDL_GetTicks();
@@ -211,6 +220,13 @@ void RE_render(struct sact_sprite *sp)
 		ERROR("Incomplete framebuffer");
 
 	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+
+	// Draw background CGs.
+	glDisable(GL_DEPTH_TEST);
+	for (int i = 0; i < RE_NR_BACK_CGS; i++)
+		render_back_cg(texture, &plugin->back_cg[i], r);
+	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fbo);
+
 	glEnable(GL_DEPTH_TEST);
 	glEnable(GL_CULL_FACE);
 
diff --git a/src/hll/ReignEngine.c b/src/hll/ReignEngine.c
index c1fb376..dbd1225 100644
--- a/src/hll/ReignEngine.c
+++ b/src/hll/ReignEngine.c
@@ -54,6 +54,14 @@ static struct motion *get_next_motion(unsigned plugin, unsigned instance)
 	return inst ? inst->next_motion : NULL;
 }
 
+static struct RE_back_cg *get_back_cg(unsigned plugin, unsigned num)
+{
+	struct RE_plugin *p = get_plugin(plugin);
+	if (!p || num >= RE_NR_BACK_CGS)
+		return NULL;
+	return &p->back_cg[num];
+}
+
 static int ReignEngine_CreatePlugin(void)
 {
 	for (int i = 0; i < RE_MAX_PLUGINS; i++) {
@@ -965,21 +973,107 @@ static bool ReignEngine_SetPostEffectFilterCr(int plugin, float cr)
 	return true;
 }
 
-//bool ReignEngine_GetBackCGName(int plugin, int num, struct string **pICGName);
-//int ReignEngine_GetBackCGNum(int plugin, int num);
-//float ReignEngine_GetBackCGBlendRate(int plugin, int num);
-//float ReignEngine_GetBackCGDestPosX(int plugin, int num);
-//float ReignEngine_GetBackCGDestPosY(int plugin, int num);
-//float ReignEngine_GetBackCGMag(int plugin, int num);
+static bool ReignEngine_GetBackCGName(int plugin, int num, struct string **cg_name)
+{
+	struct RE_back_cg* bcg = get_back_cg(plugin, num);
+	if (!bcg)
+		return false;
+	if (*cg_name)
+		free_string(*cg_name);
+	*cg_name = string_ref(bcg->name ? bcg->name : &EMPTY_STRING);
+	return true;
+}
+
+static int ReignEngine_GetBackCGNum(int plugin, int num)
+{
+	struct RE_back_cg* bcg = get_back_cg(plugin, num);
+	return bcg ? bcg->no : 0;
+}
+
+static float ReignEngine_GetBackCGBlendRate(int plugin, int num)
+{
+	struct RE_back_cg* bcg = get_back_cg(plugin, num);
+	return bcg ? bcg->blend_rate : 0.0;
+}
+
+static float ReignEngine_GetBackCGDestPosX(int plugin, int num)
+{
+	struct RE_back_cg* bcg = get_back_cg(plugin, num);
+	return bcg ? bcg->x : 0.0;
+}
+
+static float ReignEngine_GetBackCGDestPosY(int plugin, int num)
+{
+	struct RE_back_cg* bcg = get_back_cg(plugin, num);
+	return bcg ? bcg->y : 0.0;
+}
+
+static float ReignEngine_GetBackCGMag(int plugin, int num)
+{
+	struct RE_back_cg* bcg = get_back_cg(plugin, num);
+	return bcg ? bcg->mag : 0.0;
+}
+
 //float ReignEngine_GetBackCGQuakeMag(int plugin, int num);
-//bool ReignEngine_GetBackCGShow(int plugin, int num);
-HLL_WARN_UNIMPLEMENTED(true, bool, ReignEngine, SetBackCGName, int plugin, int num, struct string *pICGName /* e.g. "Data\Texture\cg29501" */);
-//bool ReignEngine_SetBackCGNum(int plugin, int num, int nCGNum);
-HLL_WARN_UNIMPLEMENTED(false, bool, ReignEngine, SetBackCGBlendRate, int plugin, int num, float blend_rate);
-HLL_WARN_UNIMPLEMENTED(true, bool, ReignEngine, SetBackCGDestPos, int plugin, int num, float fX, float fY);
-//bool ReignEngine_SetBackCGMag(int plugin, int num, float fMag);
+
+static bool ReignEngine_GetBackCGShow(int plugin, int num)
+{
+	struct RE_back_cg* bcg = get_back_cg(plugin, num);
+	return bcg ? bcg->show : false;
+}
+
+static bool ReignEngine_SetBackCGName(int plugin, int num, struct string *cg_name)
+{
+	struct RE_plugin *p = get_plugin(plugin);
+	if (!p)
+		return false;
+	return RE_back_cg_set_name(get_back_cg(plugin, num), cg_name, p->aar);
+}
+
+static bool ReignEngine_SetBackCGNum(int plugin, int num, int cg_num)
+{
+	return RE_back_cg_set(get_back_cg(plugin, num), cg_num);
+}
+
+static bool ReignEngine_SetBackCGBlendRate(int plugin, int num, float blend_rate)
+{
+	struct RE_back_cg* bcg = get_back_cg(plugin, num);
+	if (!bcg)
+		return false;
+	bcg->blend_rate = blend_rate;
+	return true;
+}
+
+static bool ReignEngine_SetBackCGDestPos(int plugin, int num, float x, float y)
+{
+	struct RE_back_cg* bcg = get_back_cg(plugin, num);
+	if (!bcg)
+		return false;
+	bcg->x = x;
+	bcg->y = y;
+	return true;
+}
+
+static bool ReignEngine_SetBackCGMag(int plugin, int num, float mag)
+{
+	struct RE_back_cg* bcg = get_back_cg(plugin, num);
+	if (!bcg)
+		return false;
+	bcg->mag = mag;
+	return true;
+}
+
 //bool ReignEngine_SetBackCGQuakeMag(int plugin, int num, float fQuakeMag);
-HLL_WARN_UNIMPLEMENTED(true, bool, ReignEngine, SetBackCGShow, int plugin, int num, bool bShow);
+
+static bool ReignEngine_SetBackCGShow(int plugin, int num, bool show)
+{
+	struct RE_back_cg* bcg = get_back_cg(plugin, num);
+	if (!bcg)
+		return false;
+	bcg->show = show;
+	return true;
+}
+
 //float ReignEngine_GetGlareBrightnessParam(int plugin, int index);
 HLL_WARN_UNIMPLEMENTED(false, bool, ReignEngine, SetGlareBrightnessParam, int plugin, int index, float param);
 //float ReignEngine_GetSSAOParam(int plugin, int type);
@@ -1313,19 +1407,19 @@ HLL_LIBRARY(ReignEngine,
 	    HLL_EXPORT(SetPostEffectFilterY, ReignEngine_SetPostEffectFilterY),
 	    HLL_EXPORT(SetPostEffectFilterCb, ReignEngine_SetPostEffectFilterCb),
 	    HLL_EXPORT(SetPostEffectFilterCr, ReignEngine_SetPostEffectFilterCr),
-	    HLL_TODO_EXPORT(GetBackCGName, ReignEngine_GetBackCGName),
-	    HLL_TODO_EXPORT(GetBackCGNum, ReignEngine_GetBackCGNum),
-	    HLL_TODO_EXPORT(GetBackCGBlendRate, ReignEngine_GetBackCGBlendRate),
-	    HLL_TODO_EXPORT(GetBackCGDestPosX, ReignEngine_GetBackCGDestPosX),
-	    HLL_TODO_EXPORT(GetBackCGDestPosY, ReignEngine_GetBackCGDestPosY),
-	    HLL_TODO_EXPORT(GetBackCGMag, ReignEngine_GetBackCGMag),
+	    HLL_EXPORT(GetBackCGName, ReignEngine_GetBackCGName),
+	    HLL_EXPORT(GetBackCGNum, ReignEngine_GetBackCGNum),
+	    HLL_EXPORT(GetBackCGBlendRate, ReignEngine_GetBackCGBlendRate),
+	    HLL_EXPORT(GetBackCGDestPosX, ReignEngine_GetBackCGDestPosX),
+	    HLL_EXPORT(GetBackCGDestPosY, ReignEngine_GetBackCGDestPosY),
+	    HLL_EXPORT(GetBackCGMag, ReignEngine_GetBackCGMag),
 	    HLL_TODO_EXPORT(GetBackCGQuakeMag, ReignEngine_GetBackCGQuakeMag),
-	    HLL_TODO_EXPORT(GetBackCGShow, ReignEngine_GetBackCGShow),
+	    HLL_EXPORT(GetBackCGShow, ReignEngine_GetBackCGShow),
 	    HLL_EXPORT(SetBackCGName, ReignEngine_SetBackCGName),
-	    HLL_TODO_EXPORT(SetBackCGNum, ReignEngine_SetBackCGNum),
+	    HLL_EXPORT(SetBackCGNum, ReignEngine_SetBackCGNum),
 	    HLL_EXPORT(SetBackCGBlendRate, ReignEngine_SetBackCGBlendRate),
 	    HLL_EXPORT(SetBackCGDestPos, ReignEngine_SetBackCGDestPos),
-	    HLL_TODO_EXPORT(SetBackCGMag, ReignEngine_SetBackCGMag),
+	    HLL_EXPORT(SetBackCGMag, ReignEngine_SetBackCGMag),
 	    HLL_TODO_EXPORT(SetBackCGQuakeMag, ReignEngine_SetBackCGQuakeMag),
 	    HLL_EXPORT(SetBackCGShow, ReignEngine_SetBackCGShow),
 	    HLL_TODO_EXPORT(GetGlareBrightnessParam, ReignEngine_GetGlareBrightnessParam),
diff --git a/src/meson.build b/src/meson.build
index 6f63698..fd4aecd 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -31,6 +31,7 @@ xsystem4 = [version_h,
             'video.c',
             'vm.c',
 
+            '3d/debug.c',
             '3d/model.c',
             '3d/parser.c',
             '3d/reign.c',