diff --git a/Makefile.mak b/Makefile.mak
index 7fcfaf50..fe5d334d 100644
--- a/Makefile.mak
+++ b/Makefile.mak
@@ -133,7 +133,7 @@ bin\th04\res_huma.com: th04\res_huma.cpp
 $**
 | masters.lib
 
-bin\th04\op.exe: bin\th04\op.obj th04\m_char.cpp bin\th04\bgimager.obj bin\th04\cdg_load.obj th04\frmdely2.c
+bin\th04\op.exe: bin\th04\op.obj th04\m_char.cpp bin\th04\bgimage.obj bin\th04\bgimager.obj bin\th04\cdg_load.obj th04\frmdely2.c
 	$(CC) $(CFLAGS) $(LARGE_LFLAGS) -DGAME=4 -DBINARY='O' -3 -Z -d -nbin\th04\ -eOP.EXE @&&|
 $**
 |
@@ -143,7 +143,7 @@ bin\th04\main.exe: bin\th04\main.obj bin\th04\scoreupd.obj th04\main011.cpp bin\
 $**
 |
 
-bin\th04\maine.exe: bin\th04\maine.obj th04\maine011.cpp bin\th04\bgimager.obj bin\th03\pi_load.obj bin\th03\pi_put_q.obj bin\th04\cdg_load.obj bin\hfliplut.obj
+bin\th04\maine.exe: bin\th04\maine.obj th04\maine011.cpp bin\th04\bgimage.obj bin\th04\bgimager.obj bin\th03\pi_load.obj bin\th03\pi_put_q.obj bin\th04\cdg_load.obj bin\hfliplut.obj
 	$(CC) $(CFLAGS) $(LARGE_LFLAGS) -DGAME=4 -DBINARY='E' -Z -nbin\th04\ -eMAINE.EXE @&&|
 $**
 |
@@ -156,7 +156,7 @@ bin\th05\res_kso.com: th05\res_kso.cpp
 $**
 | masters.lib
 
-bin\th05\op.exe: th05\op010.cpp bin\th05\op.obj th05\op011.cpp th05\m_char.cpp bin\th05\cdg_put.obj bin\th04\exit.obj bin\th05\vector.obj bin\th05\musicp_c.obj bin\th05\musicp_a.obj bin\th05\bgimager.obj bin\th05\snd_load.obj bin\th05\snd_kaja.obj bin\th05\pi_cpp_1.obj bin\th05\pi_asm_1.obj bin\th05\pi_cpp_2.obj bin\th05\pi_asm_2.obj bin\th05\initop.obj bin\th05\input_s.obj bin\th05\inp_h_w.obj bin\th05\snd_dlym.obj th05\cdg_p_nc.cpp bin\th05\frmdelay.obj bin\th04\cdg_load.obj bin\th05\egcrect.obj bin\hfliplut.obj
+bin\th05\op.exe: th05\op010.cpp bin\th05\op.obj th05\op011.cpp th05\m_char.cpp bin\th04\bgimage.obj bin\th05\cdg_put.obj bin\th04\exit.obj bin\th05\vector.obj bin\th05\musicp_c.obj bin\th05\musicp_a.obj bin\th05\bgimager.obj bin\th05\snd_load.obj bin\th05\snd_kaja.obj bin\th05\pi_cpp_1.obj bin\th05\pi_asm_1.obj bin\th05\pi_cpp_2.obj bin\th05\pi_asm_2.obj bin\th05\initop.obj bin\th05\input_s.obj bin\th05\inp_h_w.obj bin\th05\snd_dlym.obj th05\cdg_p_nc.cpp bin\th05\frmdelay.obj bin\th04\cdg_load.obj bin\th05\egcrect.obj bin\hfliplut.obj
 	$(CC) $(CFLAGS) $(LARGE_LFLAGS) -DGAME=5 -DBINARY='O' -3 -Z -nbin\th05\ -eOP.EXE @&&|
 $**
 |
@@ -166,7 +166,7 @@ bin\th05\main.exe: bin\th05\main.obj th05\main010.cpp th05\main011.cpp th05\p_co
 $**
 |
 
-bin\th05\maine.exe: bin\th05\maine.obj th05\maine011.cpp th05\regist.cpp th05\staff.cpp bin\th04\exit.obj bin\th05\vector.obj bin\th05\bgimager.obj bin\th05\snd_load.obj bin\th05\snd_kaja.obj bin\th05\pi_cpp_1.obj bin\th05\pi_asm_1.obj bin\th05\pi_cpp_2.obj bin\th05\pi_asm_2.obj bin\th05\initmain.obj bin\th05\input_s.obj bin\th05\inp_h_w.obj bin\th05\snd_dlym.obj bin\th05\frmdelay.obj bin\th04\cdg_load.obj bin\th05\egcrect.obj bin\hfliplut.obj
+bin\th05\maine.exe: bin\th05\maine.obj th05\maine011.cpp th05\regist.cpp th05\staff.cpp bin\th04\bgimage.obj bin\th04\exit.obj bin\th05\vector.obj bin\th05\bgimager.obj bin\th05\snd_load.obj bin\th05\snd_kaja.obj bin\th05\pi_cpp_1.obj bin\th05\pi_asm_1.obj bin\th05\pi_cpp_2.obj bin\th05\pi_asm_2.obj bin\th05\initmain.obj bin\th05\input_s.obj bin\th05\inp_h_w.obj bin\th05\snd_dlym.obj bin\th05\frmdelay.obj bin\th04\cdg_load.obj bin\th05\egcrect.obj bin\hfliplut.obj
 	$(CC) $(CFLAGS) $(LARGE_LFLAGS) -DGAME=5 -DBINARY='E' -Z -nbin\th05\ -eMAINE.EXE @&&|
 $**
 |
diff --git a/th04/bgimage.cpp b/th04/bgimage.cpp
new file mode 100644
index 00000000..2105a01a
--- /dev/null
+++ b/th04/bgimage.cpp
@@ -0,0 +1 @@
+#include "th04/hardware/bgimage.cpp"
diff --git a/th04/hardware/bgimage.asm b/th04/hardware/bgimage.asm
deleted file mode 100644
index c2d96730..00000000
--- a/th04/hardware/bgimage.asm
+++ /dev/null
@@ -1,88 +0,0 @@
-public BGIMAGE_SNAP
-bgimage_snap	proc far
-	push	si
-	push	di
-	cmp	bgimage_PL_B, 0
-	jnz	short @@already_allocated
-	call	hmem_allocbyte pascal, PLANE_SIZE
-	mov	bgimage_PL_B, ax
-	call	hmem_allocbyte pascal, PLANE_SIZE
-	mov	bgimage_PL_R, ax
-	call	hmem_allocbyte pascal, PLANE_SIZE
-	mov	bgimage_PL_G, ax
-	call	hmem_allocbyte pascal, PLANE_SIZE
-	mov	bgimage_PL_E, ax
-
-@@already_allocated:
-	mov	dl, 4
-	push	ds
-	push	0E000h
-	push	bgimage_PL_E
-	push	0B800h
-	push	bgimage_PL_G
-	push	0B000h
-	push	bgimage_PL_R
-	push	0A800h
-	push	bgimage_PL_B
-
-@@next_plane:
-	pop	es
-	pop	ds
-	xor	si, si
-	xor	di, di
-	mov	cx, (PLANE_SIZE / 4)
-	rep movsd
-	dec	dl
-	jnz	short @@next_plane
-	pop	ds
-	pop	di
-	pop	si
-	retf
-bgimage_snap	endp
-
-
-public BGIMAGE_PUT
-bgimage_put	proc far
-	push	si
-	push	di
-	mov	dl, 4
-	push	ds
-	push	0E000h
-	push	bgimage_PL_E
-	push	0B800h
-	push	bgimage_PL_G
-	push	0B000h
-	push	bgimage_PL_R
-	push	0A800h
-	push	bgimage_PL_B
-
-@@next_plane:
-	pop	ds
-	pop	es
-	xor	si, si
-	xor	di, di
-	mov	cx, (PLANE_SIZE / 4)
-	rep movsd
-	dec	dl
-	jnz	short @@next_plane
-	pop	ds
-	pop	di
-	pop	si
-	retf
-bgimage_put	endp
-	even
-
-
-public BGIMAGE_FREE
-bgimage_free	proc far
-	cmp	bgimage_PL_B, 0
-	jz	short @@ret
-	call	hmem_free pascal, bgimage_PL_B
-	call	hmem_free pascal, bgimage_PL_R
-	call	hmem_free pascal, bgimage_PL_G
-	call	hmem_free pascal, bgimage_PL_E
-	mov	bgimage_PL_B, 0
-
-@@ret:
-	retf
-bgimage_free	endp
diff --git a/th04/hardware/bgimage.cpp b/th04/hardware/bgimage.cpp
new file mode 100644
index 00000000..d0c312cf
--- /dev/null
+++ b/th04/hardware/bgimage.cpp
@@ -0,0 +1,82 @@
+#pragma codeseg SHARED_
+#pragma option -k-
+
+extern "C" {
+#include <mem.h>
+#include <stddef.h>
+#include "platform.h"
+#include "x86real.h"
+#include "pc98.h"
+#include "planar.h"
+#include "decomp.hpp"
+#include "master.hpp"
+#include "th04/hardware/bgimage.hpp"
+
+inline void memcpy_movsd(
+	uint16_t, uint16_t dst_off, uint16_t, uint16_t src_off, size_t size
+) {
+	_SI = src_off;
+	_DI = dst_off;
+	_CX = (size / sizeof(uint32_t));
+	REP MOVSD;
+}
+
+#define bgimage_push() __asm { \
+	push	SEG_PLANE_E; \
+	push	word ptr [bgimage.E]; \
+	push	SEG_PLANE_G; \
+	push	word ptr [bgimage.G]; \
+	push	SEG_PLANE_R; \
+	push	word ptr [bgimage.R]; \
+	push	SEG_PLANE_B; \
+	push	word ptr [bgimage.B]; \
+}
+
+void bgimage_snap(void)
+{
+	if(bgimage.B == NULL) {
+		bgimage.B = reinterpret_cast<dots8_t __seg *>(hmem_allocbyte(PLANE_SIZE));
+		bgimage.R = reinterpret_cast<dots8_t __seg *>(hmem_allocbyte(PLANE_SIZE));
+		bgimage.G = reinterpret_cast<dots8_t __seg *>(hmem_allocbyte(PLANE_SIZE));
+		bgimage.E = reinterpret_cast<dots8_t __seg *>(hmem_allocbyte(PLANE_SIZE));
+	}
+
+	_DL = PLANE_COUNT;
+	__asm {	push	ds; }
+	bgimage_push();
+	do {
+		__asm { pop 	es; }
+		__asm { pop 	ds; }
+		memcpy_movsd(_ES, 0, _DS, 0, PLANE_SIZE);
+		_DL--;
+	} while(!FLAGS_ZERO);
+	__asm { pop 	ds; }
+}
+
+void bgimage_put(void)
+{
+	_DL = PLANE_COUNT;
+	__asm {	push	ds; }
+	bgimage_push();
+	do {
+		__asm { pop 	ds; }
+		__asm { pop 	es; }
+		memcpy_movsd(_ES, 0, _DS, 0, PLANE_SIZE);
+		_DL--;
+	} while(!FLAGS_ZERO);
+	__asm { pop 	ds; }
+}
+#pragma codestring "\x90"
+
+void bgimage_free(void)
+{
+	if(bgimage.B != NULL) {
+		hmem_free(FP_SEG(bgimage.B));
+		hmem_free(FP_SEG(bgimage.R));
+		hmem_free(FP_SEG(bgimage.G));
+		hmem_free(FP_SEG(bgimage.E));
+		bgimage.B = NULL;
+	}
+}
+
+}
diff --git a/th04/hardware/bgimage.h b/th04/hardware/bgimage.hpp
similarity index 69%
rename from th04/hardware/bgimage.h
rename to th04/hardware/bgimage.hpp
index bc6e94ef..00a0617c 100644
--- a/th04/hardware/bgimage.h
+++ b/th04/hardware/bgimage.hpp
@@ -1,9 +1,12 @@
 // Additional 640×400 4-plane background image buffer.
 extern Planar<dots8_t __seg *> bgimage;
 
-void pascal bgimage_snap(void);
-void pascal bgimage_put(void);
-void pascal bgimage_free(void);
+void bgimage_snap(void);
+
+// Blits garbage data if bgimage_snap() wasn't called before.
+void bgimage_put(void);
+
+void bgimage_free(void);
 // Blits the rectangle from (⌊x/16⌋*16, y) to (⌈((x + w)/16)*16⌉, (y + h))
 // on the [bgimage] to the same position in VRAM.
 void pascal bgimage_put_rect(
diff --git a/th04/zunsoft.asm b/th04/zunsoft.asm
index c2dd358e..c201f91f 100644
--- a/th04/zunsoft.asm
+++ b/th04/zunsoft.asm
@@ -263,7 +263,7 @@ else
 endif
 	push	0
 	call	graph_copy_page
-	call	bgimage_snap
+	call	_bgimage_snap
 	graph_accesspage 1
 	call	graph_clear
 	graph_accesspage 0
@@ -420,7 +420,7 @@ frame_68:	; case 68
 	call	zunsoft_pyro_new
 
 @@no_new_pyro_this_frame:
-	call	bgimage_put	; default
+	call	_bgimage_put	; default
 	call	zunsoft_update_and_render
 if GAME eq 4
 	call	_input_reset_sense
@@ -475,7 +475,7 @@ endif
 
 @@ret:
 	call	super_free
-	call	bgimage_free
+	call	_bgimage_free
 	pop	di
 	pop	si
 	leave
diff --git a/th04_maine.asm b/th04_maine.asm
index e2f999f0..5a6ffdae 100644
--- a/th04_maine.asm
+++ b/th04_maine.asm
@@ -2344,7 +2344,7 @@ sub_B44D	proc near
 		call	pi_put_8 pascal, large 0, 0
 		freePISlotLarge	0
 		call	graph_copy_page pascal, 0
-		call	bgimage_snap
+		call	_bgimage_snap
 		kajacall	KAJA_SONG_STOP
 		call	snd_load pascal, ds, offset aStaff, SND_LOAD_SONG
 		kajacall	KAJA_SONG_PLAY
@@ -2392,7 +2392,7 @@ sub_B44D	proc near
 		call	pi_put_8 pascal, large 0, 0
 		freePISlotLarge	0
 		call	graph_copy_page pascal, 0
-		call	bgimage_snap
+		call	_bgimage_snap
 		push	4
 		call	palette_black_in
 		call	cdg_load_single pascal, 2, ds, offset aSff4_cdg, 0
@@ -2455,7 +2455,7 @@ sub_B44D	proc near
 		call	sub_B291
 		push	3000A0h
 		call	snd_delay_until_measure
-		call	bgimage_free
+		call	_bgimage_free
 		call	cdg_free_all
 		push	4
 		call	palette_black_out
@@ -4615,7 +4615,8 @@ include th02/initmain.asm
 		db    0
 include th04/hardware/input_s.asm
 include th04/snd/se.asm
-include th04/hardware/bgimage.asm
+	extern _bgimage_snap:proc
+	extern _bgimage_free:proc
 	extern BGIMAGE_PUT_RECT:proc
 	extern CDG_LOAD_SINGLE_NOALPHA:proc
 	extern CDG_LOAD_SINGLE:proc
diff --git a/th04_op.asm b/th04_op.asm
index 3c2a572e..eb79c6b3 100644
--- a/th04_op.asm
+++ b/th04_op.asm
@@ -1811,7 +1811,7 @@ _musicroom	proc near
 		mov	_music_sel, al
 		call	draw_tracks pascal, word ptr _music_sel
 		call	graph_copy_page pascal, 0
-		call	bgimage_snap
+		call	_bgimage_snap
 		graph_accesspage 1
 		graph_showpage 0
 		call	screen_back_B_snap
@@ -1917,7 +1917,7 @@ loc_C544:
 		graph_accesspage al
 		push	1
 		call	palette_black_out
-		call	bgimage_free
+		call	_bgimage_free
 		call	snd_load pascal, ds, offset aOp_2, SND_LOAD_SONG
 		kajacall	KAJA_SONG_PLAY
 		pop	bp
@@ -2667,10 +2667,12 @@ include th04/formats/cdg_put_noalpha.asm
 include th04/hardware/input_s.asm
 include th04/snd/se.asm
 include th04/hardware/egcrect.asm
-include th04/hardware/bgimage.asm
 SHARED	ends
 
 SHARED_	segment	word public 'CODE' use16
+	extern _bgimage_snap:proc
+	extern _bgimage_put:proc
+	extern _bgimage_free:proc
 	extern BGIMAGE_PUT_RECT:proc
 	extern CDG_LOAD_ALL_NOALPHA:proc
 	extern CDG_LOAD_ALL:proc
diff --git a/th05/m_char.cpp b/th05/m_char.cpp
index 46915397..2c018d47 100644
--- a/th05/m_char.cpp
+++ b/th05/m_char.cpp
@@ -14,7 +14,7 @@ extern "C" {
 #include "th01/ranks.h"
 #include "th02/hardware/frmdelay.h"
 #include "th04/formats/cdg.h"
-#include "th04/hardware/bgimage.h"
+#include "th04/hardware/bgimage.hpp"
 #include "th04/score.h"
 #include "th04/common.h"
 #include "th05/chars.h"
diff --git a/th05_maine.asm b/th05_maine.asm
index 35eadfa8..bc318716 100644
--- a/th05_maine.asm
+++ b/th05_maine.asm
@@ -980,7 +980,7 @@ loc_ACAA:
 		call	graph_clear
 		graph_accesspage 0
 		call	graph_clear
-		call	bgimage_snap
+		call	_bgimage_snap
 		jmp	loc_AF8F	; default
 ; ---------------------------------------------------------------------------
 
@@ -1004,7 +1004,7 @@ loc_ACF4:
 		call	pi_put_8 pascal, large 0, 0
 		call	graph_copy_page pascal, 0
 		graph_accesspage 0
-		call	bgimage_snap
+		call	_bgimage_snap
 		jmp	loc_AF8F	; default
 ; ---------------------------------------------------------------------------
 
@@ -1492,7 +1492,7 @@ loc_B18D:
 ; ---------------------------------------------------------------------------
 
 loc_B196:
-		call	bgimage_free
+		call	_bgimage_free
 		call	pi_free pascal, 0
 		pop	si
 		leave
@@ -3465,7 +3465,7 @@ loc_C2BB:
 		call	graph_putsa_fx pascal, (120 shl 16) or 192, 2, ds, offset aGxgnbGvbGhvV_0
 
 loc_C2EB:
-		call	bgimage_snap
+		call	_bgimage_snap
 		les	bx, _resident
 		cmp	es:[bx+resident_t.end_sequence], ES_EXTRA
 		jb	short loc_C307
@@ -3475,7 +3475,7 @@ loc_C2EB:
 
 loc_C307:
 		call	graph_copy_page pascal, 1
-		call	bgimage_snap
+		call	_bgimage_snap
 		kajacall	KAJA_SONG_STOP
 		call	snd_load pascal, ds, offset aName, SND_LOAD_SONG
 		kajacall	KAJA_SONG_PLAY
@@ -3779,7 +3779,7 @@ loc_C5C3:
 		call	input_wait_for_change pascal, 0
 
 loc_C5CD:
-		call	bgimage_free
+		call	_bgimage_free
 		call	super_free
 		call	text_clear
 		push	1
@@ -7531,7 +7531,8 @@ include th04/snd/detmodes.asm
 include th04/hardware/grppsafx.asm
 include th04/formats/cdg_put_noalpha.asm
 include th04/snd/se.asm
-include th04/hardware/bgimage.asm
+	extern _bgimage_snap:proc
+	extern _bgimage_free:proc
 	extern _game_exit:proc
 	extern VECTOR2_AT:proc
 	extern BGIMAGE_PUT_RECT:proc
diff --git a/th05_op.asm b/th05_op.asm
index 27f6d4f6..8cc7aadc 100644
--- a/th05_op.asm
+++ b/th05_op.asm
@@ -1926,7 +1926,7 @@ _musicroom	proc near
 		call	pi_free pascal, 0
 		call	_piano_setup_and_put_initial
 		call	screen_back_B_snap
-		call	bgimage_snap
+		call	_bgimage_snap
 		call	draw_tracks pascal, word ptr _music_sel
 		call	graph_copy_page pascal, 0
 		graph_accesspage 1
@@ -2138,7 +2138,7 @@ loc_C790:
 		graph_accesspage al
 		push	1
 		call	palette_black_out
-		call	bgimage_free
+		call	_bgimage_free
 		call	snd_load pascal, ds, offset aH_op+2, SND_LOAD_SONG
 		kajacall	KAJA_SONG_PLAY
 		pop	si
@@ -2532,7 +2532,9 @@ include th02/exit_dos.asm
 include th04/hardware/grppsafx.asm
 include th04/formats/cdg_put_noalpha.asm
 include th04/snd/se.asm
-include th04/hardware/bgimage.asm
+	extern _bgimage_snap:proc
+	extern _bgimage_put:proc
+	extern _bgimage_free:proc
 	extern CDG_PUT_8:proc
 	extern _game_exit:proc
 	extern VECTOR1_AT:proc