diff --git a/th04/main/boss/impl.hpp b/th04/main/boss/impl.hpp
index dec8171e..fac15f5c 100644
--- a/th04/main/boss/impl.hpp
+++ b/th04/main/boss/impl.hpp
@@ -44,3 +44,24 @@
 		tiles_render_after_custom(boss.phase_frame); \
 	}  \
 }
+
+// Like boss_bg_render_entrance_bb_opaque_and_backdrop(), but rendering 3) as
+// a transition between stage tiles (where the entrance .BB bit is 0) and the
+// backdrop image (where the entrance .BB bit is 1).
+#define boss_bg_render_entrance_bb_transition_and_backdrop( \
+	on_hp_fill, backdrop_left, backdrop_top, backdrop_col \
+) { \
+	if(boss.phase == PHASE_BOSS_HP_FILL) { \
+		on_hp_fill; \
+	} else if(boss.phase == PHASE_BOSS_ENTRANCE_BB) { \
+		boss_backdrop_render(backdrop_left, backdrop_top, backdrop_col); \
+		tiles_bb_invalidate(bb_boss_seg, (boss.phase_frame / 2)); \
+		tiles_redraw_invalidated(); \
+	} else if(boss.phase < PHASE_BOSS_EXPLODE_BIG) { \
+		boss_backdrop_render(backdrop_left, backdrop_top, backdrop_col); \
+	} else if(boss.phase == PHASE_BOSS_EXPLODE_BIG) { \
+		tiles_render_all(); \
+	} else /* if(boss.phase == PHASE_NONE) */ { \
+		tiles_render_after_custom(boss.phase_frame); \
+	} \
+}
diff --git a/th05/main/boss/bosses.hpp b/th05/main/boss/bosses.hpp
index 63f73c1e..0b641d40 100644
--- a/th05/main/boss/bosses.hpp
+++ b/th05/main/boss/bosses.hpp
@@ -6,6 +6,12 @@
 // Image coordinates
 // -----------------
 
+static const pixel_t SARA_BACKDROP_W = 320;
+static const screen_x_t SARA_BACKDROP_LEFT = (
+	PLAYFIELD_LEFT + (PLAYFIELD_W / 2) - (SARA_BACKDROP_W / 2)
+);
+static const screen_y_t SARA_BACKDROP_TOP = PLAYFIELD_TOP;
+
 static const screen_x_t LOUISE_BACKDROP_LEFT = PLAYFIELD_LEFT;
 static const screen_y_t LOUISE_BACKDROP_TOP = PLAYFIELD_TOP;
 
diff --git a/th05/main/boss/render.cpp b/th05/main/boss/render.cpp
index fdee22ee..4b21c7c5 100644
--- a/th05/main/boss/render.cpp
+++ b/th05/main/boss/render.cpp
@@ -66,6 +66,16 @@ extern boss_particle_t boss_particles[BOSS_PARTICLE_COUNT];
 extern lineset_t linesets[LINESET_COUNT];
 /// ----------
 
+void pascal near sara_bg_render(void)
+{
+	boss_bg_render_entrance_bb_transition_and_backdrop(
+		tiles_render_after_custom(boss.phase_frame),
+		SARA_BACKDROP_LEFT,
+		SARA_BACKDROP_TOP,
+		0
+	);
+}
+
 void pascal near louise_bg_render(void)
 {
 	boss_bg_render_entrance_bb_opaque_and_backdrop(
diff --git a/th05_main.asm b/th05_main.asm
index b1889a2c..0c29ca54 100644
--- a/th05_main.asm
+++ b/th05_main.asm
@@ -2810,64 +2810,7 @@ loc_D060:
 sub_D032	endp
 
 include th04/main/boss/backdrop.asm
-
-; =============== S U B	R O U T	I N E =======================================
-
-; Attributes: bp-based frame
-
-public @SARA_BG_RENDER$QV
-@sara_bg_render$qv	proc near
-		push	bp
-		mov	bp, sp
-		cmp	_boss_phase, PHASE_BOSS_HP_FILL
-		jnz	short loc_D09F
-		cmp	_boss_phase_frame, 2
-		jg	short loc_D0EF
-		jmp	short loc_D0EA
-; ---------------------------------------------------------------------------
-
-loc_D09F:
-		cmp	_boss_phase, PHASE_BOSS_ENTRANCE_BB
-		jnz	short loc_D0C8
-		call	@boss_backdrop_render$qiic pascal, (64 shl 16) or 16, 0
-		mov	ax, _bb_boss_seg
-		mov	_tiles_bb_seg, ax
-		mov	ax, _boss_phase_frame
-		cwd
-		sub	ax, dx
-		sar	ax, 1
-		call	@tiles_bb_invalidate_raw$qi pascal, ax
-		call	tiles_redraw_invalidated
-		pop	bp
-		retn
-; ---------------------------------------------------------------------------
-
-loc_D0C8:
-		cmp	_boss_phase, PHASE_BOSS_EXPLODE_BIG
-		jnb	short loc_D0DC
-		call	@boss_backdrop_render$qiic pascal, (64 shl 16) or 16, 0
-		pop	bp
-		retn
-; ---------------------------------------------------------------------------
-
-loc_D0DC:
-		cmp	_boss_phase, PHASE_BOSS_EXPLODE_BIG
-		jz	short loc_D0EA
-		cmp	_boss_phase_frame, 2
-		jg	short loc_D0EF
-
-loc_D0EA:
-		call	tiles_render_all
-		pop	bp
-		retn
-; ---------------------------------------------------------------------------
-
-loc_D0EF:
-		call	tiles_render
-		pop	bp
-		retn
-@sara_bg_render$qv	endp
-
+	@SARA_BG_RENDER$QV procdesc pascal near
 	@LOUISE_BG_RENDER$QV procdesc pascal near
 	@ALICE_BG_RENDER$QV procdesc pascal near
 	@MAI_YUKI_BG_RENDER$QV procdesc pascal near