diff --git a/Makefile.mak b/Makefile.mak
index 3efd5357..2497a985 100644
--- a/Makefile.mak
+++ b/Makefile.mak
@@ -126,7 +126,7 @@ bin\th04\op.exe: bin\th04\op.obj th04\m_char.cpp bin\th01\vplanset.obj bin\th02\
 $**
 |
 
-bin\th04\main.exe: bin\th04\main.obj bin\th04\slowdown.obj th04\ems.cpp th04\playfld.cpp th04\f_dialog.cpp th04\dialog.cpp bin\th04\player_p.obj bin\th04\scoreupd.obj th04\hud_ovrl.cpp bin\th04\cfg_lres.obj bin\th01\vplanset.obj bin\th03\vector2.obj bin\th02\frmdely1.obj bin\th03\hfliplut.obj th04\mpn_free.cpp bin\th04\input_w.obj th04\mpn_l_i.cpp bin\th04\vector.obj bin\th04\snd_pmdr.obj bin\th04\snd_mmdr.obj bin\th04\snd_kaja.obj bin\th04\snd_mode.obj bin\th04\snd_load.obj bin\th04\cdg_put.obj bin\th04\exit.obj bin\th04\initmain.obj bin\th04\cdg_p_na.obj bin\th04\cdg_p_pr.obj bin\th04\input_s.obj bin\th04\snd_se_r.obj bin\th04\snd_se.obj bin\th04\cdg_load.obj th04\gather.cpp bin\th04\scrolly3.obj bin\th04\motion_3.obj th04\mb_dft.cpp bin\th04\it_spl_u.obj th04\bullet_u.cpp th04\bullet_a.cpp th04\boss.cpp th04\boss_4r.cpp th04\boss_x2.cpp
+bin\th04\main.exe: bin\th04\main.obj bin\th04\slowdown.obj th04\ems.cpp th04\playfld.cpp th04\f_dialog.cpp th04\dialog.cpp bin\th04\player_p.obj bin\th04\scoreupd.obj th04\hud_ovrl.cpp bin\th04\cfg_lres.obj bin\th01\vplanset.obj bin\th03\vector2.obj bin\th02\frmdely1.obj bin\th03\hfliplut.obj th04\mpn_free.cpp bin\th04\input_w.obj th04\mpn_l_i.cpp bin\th04\vector.obj bin\th04\snd_pmdr.obj bin\th04\snd_mmdr.obj bin\th04\snd_kaja.obj bin\th04\snd_mode.obj bin\th04\snd_load.obj bin\th04\cdg_put.obj bin\th04\exit.obj bin\th04\initmain.obj bin\th04\cdg_p_na.obj bin\th04\cdg_p_pr.obj bin\th04\input_s.obj bin\th04\snd_se_r.obj bin\th04\snd_se.obj bin\th04\cdg_load.obj th04\gather.cpp bin\th04\scrolly3.obj bin\th04\motion_3.obj th04\mb_dft.cpp bin\th04\it_spl_u.obj th04\boss_4m.cpp th04\bullet_u.cpp th04\bullet_a.cpp th04\boss.cpp th04\boss_4r.cpp th04\boss_x2.cpp
 	$(CC) $(CFLAGS) $(LARGE_LFLAGS) -DGAME=4 -DBINARY='M' -3 -Z -nbin\th04\ -eMAIN.EXE @&&|
 $**
 |
diff --git a/th04/boss_4m.cpp b/th04/boss_4m.cpp
new file mode 100644
index 00000000..c4418bee
--- /dev/null
+++ b/th04/boss_4m.cpp
@@ -0,0 +1 @@
+#include "th04/main/boss/b4m.cpp"
diff --git a/th04/main/boss/b4m.cpp b/th04/main/boss/b4m.cpp
new file mode 100644
index 00000000..c22fcb94
--- /dev/null
+++ b/th04/main/boss/b4m.cpp
@@ -0,0 +1,59 @@
+/// Stage 4 Boss - Marisa
+/// ---------------------
+
+#include "platform.h"
+#include "pc98.h"
+#include "th01/math/subpixel.hpp"
+#include "th04/math/motion.hpp"
+extern "C" {
+#include "th04/main/playfld.hpp"
+}
+#include "th04/main/phase.hpp"
+#include "th04/main/boss/boss.hpp"
+
+/// State
+/// -----
+
+#define flystep_pointreflected_frame boss_statebyte[13]
+/// -----
+
+// On [flystep_pointreflected_frame] 0, this function sets up [boss] movement
+// towards the point reflection of Marisa's position across a fixed position
+// near the top of the sealed moon in the background. The velocity is
+// calculated to reach this exact point at [duration - 12], with Marisa braking
+// on the last 12 frames by halving that velocity each frame. Every call to
+// this function, including the one on frame 0, then applies this velocity to
+// [boss].
+// [duration] values <12 will move Marisa into the opposite direction instead.
+// Returns `true` if the function was called for [duration] frames.
+//
+// ZUN bug: Not defined for [duration] values of 12 or 13, which will crash the
+// game with a division by zero ("Divide Error"). The two patterns that pass a
+// variable [duration] to this function also only happen to call this function
+// every 4 frames rather than every frame, introducing additional jerkiness.
+bool pascal near marisa_flystep_pointreflected(int duration)
+{
+	enum {
+		POINT_X = TO_SP(PLAYFIELD_W / 2),
+		POINT_Y = TO_SP((PLAYFIELD_H * 7) / 23),
+		BRAKE_DURATION = 12,
+	};
+	if(flystep_pointreflected_frame == 0) {
+		boss.pos.velocity.x.v = (
+			(POINT_X - boss.pos.cur.x) / ((duration / 2) - (BRAKE_DURATION / 2))
+		);
+		boss.pos.velocity.y.v = (
+			(POINT_Y - boss.pos.cur.y) / ((duration / 2) - (BRAKE_DURATION / 2))
+		);
+	}
+	flystep_pointreflected_frame++;
+	if(flystep_pointreflected_frame >= (duration - BRAKE_DURATION)) {
+		boss.pos.velocity.x.v /= 2;
+		boss.pos.velocity.y.v /= 2;
+	}
+	if(flystep_pointreflected_frame >= duration) {
+		return true;
+	}
+	boss.pos.update_seg3();
+	return false;
+}
diff --git a/th04_main.asm b/th04_main.asm
index fe9415ce..277f319e 100644
--- a/th04_main.asm
+++ b/th04_main.asm
@@ -45,7 +45,7 @@ include th04/main/enemy/enemy.inc
 
 main_01 group SLOWDOWN_TEXT, ma_TEXT, EMS_TEXT, mai_TEXT, PLAYFLD_TEXT, main_TEXT, DIALOG_TEXT, main__TEXT, PLAYER_P_TEXT, main_0_TEXT, HUD_OVRL_TEXT, main_01_TEXT, main_012_TEXT, CFG_LRES_TEXT, main_013_TEXT
 g_SHARED group SHARED, SHARED_
-main_03 group GATHER_TEXT, SCROLLY3_TEXT, MOTION_3_TEXT, main_032_TEXT, IT_SPL_U_TEXT, main_033_TEXT, MB_DFT_TEXT, main_034_TEXT, BULLET_U_TEXT, BULLET_A_TEXT, main_035_TEXT, BOSS_TEXT, main_036_TEXT
+main_03 group GATHER_TEXT, SCROLLY3_TEXT, MOTION_3_TEXT, main_032_TEXT, IT_SPL_U_TEXT, BOSS_4M_TEXT, main_033_TEXT, MB_DFT_TEXT, main_034_TEXT, BULLET_U_TEXT, BULLET_A_TEXT, main_035_TEXT, BOSS_TEXT, main_036_TEXT
 
 ; ===========================================================================
 
@@ -12081,7 +12081,7 @@ IT_SPL_U_TEXT	segment	word public 'CODE' use16
 	@item_splashes_update$qv procdesc pascal near
 IT_SPL_U_TEXT	ends
 
-main_033_TEXT	segment	word public 'CODE' use16
+BOSS_4M_TEXT	segment	word public 'CODE' use16
 
 ; =============== S U B	R O U T	I N E =======================================
 
@@ -16758,84 +16758,11 @@ loc_16B7D:
 		retn
 marisa_16AE9	endp
 
+	@MARISA_FLYSTEP_POINTREFLECTED$QI procdesc pascal near \
+		duration:word
+BOSS_4M_TEXT	ends
 
-; =============== S U B	R O U T	I N E =======================================
-
-; Attributes: bp-based frame
-
-marisa_16B85	proc near
-
-arg_0		= word ptr  4
-
-		push	bp
-		mov	bp, sp
-		push	si
-		mov	si, [bp+arg_0]
-		cmp	_boss_statebyte[13].BSB_motion_lerp_frames, 0
-		jnz	short loc_16BC5
-		mov	ax, si
-		cwd
-		sub	ax, dx
-		sar	ax, 1
-		add	ax, -6
-		push	ax
-		mov	ax, (192 shl 4)
-		sub	ax, _boss_pos.cur.x
-		cwd
-		pop	bx
-		idiv	bx
-		mov	_boss_pos.velocity.x, ax
-		mov	ax, si
-		cwd
-		sub	ax, dx
-		sar	ax, 1
-		add	ax, -6
-		push	ax
-		mov	ax, (112 shl 4)
-		sub	ax, _boss_pos.cur.y
-		cwd
-		pop	bx
-		idiv	bx
-		mov	_boss_pos.velocity.y, ax
-
-loc_16BC5:
-		inc	_boss_statebyte[13].BSB_motion_lerp_frames
-		mov	al, _boss_statebyte[13].BSB_motion_lerp_frames
-		mov	ah, 0
-		lea	dx, [si-0Ch]
-		cmp	ax, dx
-		jl	short loc_16BEB
-		mov	ax, _boss_pos.velocity.x
-		cwd
-		sub	ax, dx
-		sar	ax, 1
-		mov	_boss_pos.velocity.x, ax
-		mov	ax, _boss_pos.velocity.y
-		cwd
-		sub	ax, dx
-		sar	ax, 1
-		mov	_boss_pos.velocity.y, ax
-
-loc_16BEB:
-		mov	al, _boss_statebyte[13].BSB_motion_lerp_frames
-		mov	ah, 0
-		cmp	ax, si
-		jl	short loc_16BF8
-		mov	al, 1
-		jmp	short loc_16C00
-; ---------------------------------------------------------------------------
-
-loc_16BF8:
-		push	offset _boss_pos
-		call	@PlayfieldMotion@update_seg3$qv
-		mov	al, 0
-
-loc_16C00:
-		pop	si
-		pop	bp
-		retn	2
-marisa_16B85	endp
-
+main_033_TEXT	segment	byte public 'CODE' use16
 
 ; =============== S U B	R O U T	I N E =======================================
 
@@ -17314,8 +17241,7 @@ loc_16FC6:
 		mov	ah, 0
 		mov	dx, 160
 		sub	dx, ax
-		push	dx
-		call	marisa_16B85
+		call	@marisa_flystep_pointreflected$qi pascal, dx
 		mov	_bullet_template.spawn_type, BST_BULLET16
 		mov	_bullet_template.patnum, PAT_BULLET16_D_BLUE
 		mov	_bullet_template.speed, (3 shl 4) + 4
@@ -17463,8 +17389,7 @@ loc_17102:
 		mov	ah, 0
 		mov	dx, 160
 		sub	dx, ax
-		push	dx
-		call	marisa_16B85
+		call	@marisa_flystep_pointreflected$qi pascal, dx
 		mov	_bullet_template.spawn_type, BST_BULLET16
 		mov	_bullet_template.patnum, PAT_BULLET16_N_STAR
 		mov	_bullet_template.BT_group, BG_SPREAD_AIMED
@@ -17628,8 +17553,7 @@ loc_17266:
 ; ---------------------------------------------------------------------------
 
 loc_1726E:
-		push	60h
-		call	marisa_16B85
+		call	@marisa_flystep_pointreflected$qi pascal, 96
 		cmp	_boss_statebyte[15].BSB_subpattern_num, 0
 		jnz	short loc_1729F
 		mov	_boss_statebyte[15].BSB_subpattern_num, 1
@@ -17776,8 +17700,7 @@ loc_173CB:
 ; ---------------------------------------------------------------------------
 
 loc_173D3:
-		push	40h
-		call	marisa_16B85
+		call	@marisa_flystep_pointreflected$qi pascal, 64
 		or	al, al
 		jnz	loc_1747D
 		mov	ax, _boss_phase_frame
@@ -18025,8 +17948,7 @@ loc_1760D:
 ; ---------------------------------------------------------------------------
 
 loc_17615:
-		push	80h
-		call	marisa_16B85
+		call	@marisa_flystep_pointreflected$qi pascal, 128
 		cmp	_boss_statebyte[15].BSB_bitless_pattern_started, 0
 		jnz	short loc_17634
 		call	randring2_next16_and pascal, 1Fh
@@ -18164,8 +18086,7 @@ loc_17794:
 ; ---------------------------------------------------------------------------
 
 loc_1779E:
-		push	0A0h
-		call	marisa_16B85
+		call	@marisa_flystep_pointreflected$qi pascal, 160
 		cmp	_boss_statebyte[15].BSB_bitless_pattern_started, 0
 		jnz	short loc_177B8
 		call	randring2_next16_and pascal, 1Fh
@@ -18359,8 +18280,7 @@ loc_17958:
 ; ---------------------------------------------------------------------------
 
 loc_1795F:
-		push	48h ; 'H'
-		call	marisa_16B85
+		call	@marisa_flystep_pointreflected$qi pascal, 72
 		or	al, al
 		jnz	short loc_179A8
 		mov	ax, _boss_phase_frame
@@ -18489,7 +18409,7 @@ loc_17A75:
 		mov	byte_25674, 0
 		mov	byte_2566E, 0Ah
 		mov	byte_2566F, 0
-		mov	_boss_statebyte[13].BSB_motion_lerp_frames, 0
+		mov	_boss_statebyte[13].BSB_flystep_pointreflected_frame, 0
 		jmp	loc_17CA4
 ; ---------------------------------------------------------------------------
 
@@ -18567,7 +18487,7 @@ loc_17B1E:
 		cmp	_boss_phase_frame, 64
 		jl	short loc_17B98	; default
 		inc	_boss_mode_change
-		mov	_boss_statebyte[13].BSB_motion_lerp_frames, 0
+		mov	_boss_statebyte[13].BSB_flystep_pointreflected_frame, 0
 		cmp	byte_2566F, 0
 		jnz	short loc_17B62
 		cmp	byte_25672, 0
@@ -32388,35 +32308,35 @@ byte_2D00E	db ?
 include th04/main/boss/funcs[bss].asm
 
 boss_statebyte_t union
-	BSB_angle_mirror_y           	db ?
-	BSB_bitless_pattern_started  	db ?
-	BSB_cluster_angle            	db ?
-	BSB_delta_angle_between_rings	db ?
-	BSB_direction                	db ?
-	BSB_gengetsu_started         	db ?
-	BSB_motion_lerp_frames         	db ?
-	BSB_orb_count                	db ?
-	BSB_orb_interval             	db ?
-	BSB_origin_offset_x          	db ? ; pixel_t
-	BSB_phase_frame              	db ?
-	BSB_pattern_num_prev         	db ?
-	BSB_patterns_done            	db ?
-	BSB_pellet_stack_angle       	db ?
-	BSB_thicklaser_radius        	db ?
-	BSB_spread                   	db ?
-	BSB_spread_angle             	db ?
-	BSB_spread_angle_range       	db ?
-	BSB_spread_delta_angle       	db ?
-	BSB_spread_interval          	db ?
-	BSB_spread_speed             	db ?
-	BSB_spread_turns_max         	db ?
-	BSB_spin_ring                	db ?
-	BSB_stack                    	db ?
-	BSB_stack_left_angle         	db ?
-	BSB_stack_right_angle        	db ?
-	BSB_stacks_fired             	db ?
-	BSB_subpattern_id            	db ?
-	BSB_subpattern_num           	db ?
+	BSB_angle_mirror_y              	db ?
+	BSB_bitless_pattern_started     	db ?
+	BSB_cluster_angle               	db ?
+	BSB_delta_angle_between_rings   	db ?
+	BSB_direction                   	db ?
+	BSB_gengetsu_started            	db ?
+	BSB_flystep_pointreflected_frame	db ?
+	BSB_orb_count                   	db ?
+	BSB_orb_interval                	db ?
+	BSB_origin_offset_x             	db ? ; pixel_t
+	BSB_phase_frame                 	db ?
+	BSB_pattern_num_prev            	db ?
+	BSB_patterns_done               	db ?
+	BSB_pellet_stack_angle          	db ?
+	BSB_thicklaser_radius           	db ?
+	BSB_spread                      	db ?
+	BSB_spread_angle                	db ?
+	BSB_spread_angle_range          	db ?
+	BSB_spread_delta_angle          	db ?
+	BSB_spread_interval             	db ?
+	BSB_spread_speed                	db ?
+	BSB_spread_turns_max            	db ?
+	BSB_spin_ring                   	db ?
+	BSB_stack                       	db ?
+	BSB_stack_left_angle            	db ?
+	BSB_stack_right_angle           	db ?
+	BSB_stacks_fired                	db ?
+	BSB_subpattern_id               	db ?
+	BSB_subpattern_num              	db ?
 boss_statebyte_t ends
 
 public _boss_statebyte