diff --git a/Makefile.mak b/Makefile.mak
index 01863b07..070e19fd 100644
--- a/Makefile.mak
+++ b/Makefile.mak
@@ -149,7 +149,7 @@ bin\th05\op.exe: th05\op010.cpp bin\th05\op.obj th05\op011.cpp th05\m_char.cpp b
 $**
 |
 
-bin\th05\main.exe: bin\th05\main.obj bin\th04\slowdown.obj th05\ems.cpp bin\th05\cfg_lres.obj th05\main010.cpp th05\f_dialog.cpp th05\dialog.cpp th05\playfld.cpp th05\main011.cpp th05\p_common.cpp th05\p_reimu.cpp th05\p_marisa.cpp th05\p_mima.cpp th05\p_yuuka.cpp bin\th05\player.obj bin\th05\hud_bar.obj bin\th05\scoreupd.obj th05\hud_ovrl.cpp bin\th04\player_p.obj th05\player_a.cpp bin\th05\bullet_1.obj th05\bullet_c.cpp bin\th03\vector2.obj bin\th03\hfliplut.obj bin\th04\snd_pmdr.obj bin\th04\snd_mmdr.obj bin\th04\snd_mode.obj bin\th05\bullet.obj th05\bullet_t.cpp bin\th04\cdg_p_na.obj bin\th04\snd_se_r.obj bin\th04\snd_se.obj bin\th05\cdg_put.obj bin\th04\exit.obj bin\th05\vector.obj bin\th05\snd_load.obj bin\th05\snd_kaja.obj bin\th05\initmain.obj bin\th05\input_s.obj bin\th05\inp_h_w.obj bin\th05\frmdelay.obj bin\th04\cdg_load.obj bin\th04\scrolly3.obj bin\th04\motion_3.obj th05\gather.cpp th05\main032.cpp th05\mb_dft.cpp th05\laser_sc.cpp th05\cheeto_u.cpp bin\th04\it_spl_u.obj th05\bullet_u.cpp th05\main034.cpp th05\boss_6.cpp th05\boss_x.cpp th05\boss.cpp th05\main014.cpp
+bin\th05\main.exe: bin\th05\main.obj bin\th04\slowdown.obj th05\ems.cpp bin\th05\cfg_lres.obj th05\main010.cpp th05\f_dialog.cpp th05\dialog.cpp th05\playfld.cpp th05\main011.cpp th05\p_common.cpp th05\p_reimu.cpp th05\p_marisa.cpp th05\p_mima.cpp th05\p_yuuka.cpp bin\th05\player.obj bin\th05\hud_bar.obj bin\th05\scoreupd.obj th05\hud_ovrl.cpp bin\th04\player_p.obj th05\player_a.cpp bin\th05\bullet_1.obj th05\bullet_c.cpp bin\th03\vector2.obj bin\th03\hfliplut.obj bin\th04\snd_pmdr.obj bin\th04\snd_mmdr.obj bin\th04\snd_mode.obj bin\th05\bullet.obj th05\bullet_t.cpp bin\th04\cdg_p_na.obj bin\th04\snd_se_r.obj bin\th04\snd_se.obj bin\th05\cdg_put.obj bin\th04\exit.obj bin\th05\vector.obj bin\th05\snd_load.obj bin\th05\snd_kaja.obj bin\th05\initmain.obj bin\th05\input_s.obj bin\th05\inp_h_w.obj bin\th05\frmdelay.obj bin\th04\cdg_load.obj bin\th04\scrolly3.obj bin\th04\motion_3.obj th05\gather.cpp th05\main032.cpp th05\mb_dft.cpp th05\laser_sc.cpp th05\cheeto_u.cpp bin\th04\it_spl_u.obj th05\bullet_u.cpp th05\midboss1.cpp th05\main034.cpp th05\boss_6.cpp th05\boss_x.cpp th05\boss.cpp th05\main014.cpp
 	$(CC) $(CFLAGS) $(LARGE_LFLAGS) -3 -Z -DGAME=5 -DBINARY='M' -nbin\th05\ -eMAIN.EXE @&&|
 $**
 |
diff --git a/th05/main/midboss/m1.cpp b/th05/main/midboss/m1.cpp
new file mode 100644
index 00000000..b9e7f6ef
--- /dev/null
+++ b/th05/main/midboss/m1.cpp
@@ -0,0 +1,37 @@
+/// Stage 1 midboss
+/// ---------------
+
+#include "platform.h"
+#include "pc98.h"
+#include "master.hpp"
+#include "th01/math/subpixel.hpp"
+#include "th04/math/motion.hpp"
+extern "C" {
+#include "th04/math/vector.hpp"
+#include "th04/main/playfld.hpp"
+}
+#include "th04/main/midboss/midboss.hpp"
+
+// State
+// -----
+
+#define distance_from_center midboss.pos.velocity.x
+// -----
+
+void near midboss1_move(void)
+{
+	midboss.pos.prev.x = midboss.pos.cur.x;
+	midboss.pos.prev.y = midboss.pos.cur.y;
+
+	midboss.pos.cur.x.v = vector1_at(
+		to_sp(playfield_fraction_x(1 / 2.0f)),
+		distance_from_center,
+		CosTable8[midboss.angle]
+	);
+	midboss.pos.cur.y.v = vector1_at(
+		to_sp(playfield_fraction_y(6 / 23.0f)),
+		distance_from_center,
+		SinTable8[midboss.angle]
+	);
+	midboss.angle -= 0x02;
+}
diff --git a/th05/midboss1.cpp b/th05/midboss1.cpp
new file mode 100644
index 00000000..72ab5798
--- /dev/null
+++ b/th05/midboss1.cpp
@@ -0,0 +1 @@
+#include "th05/main/midboss/m1.cpp"
diff --git a/th05_main.asm b/th05_main.asm
index 42c9a4f2..845abc4d 100644
--- a/th05_main.asm
+++ b/th05_main.asm
@@ -39,7 +39,7 @@ include th05/main/enemy/enemy.inc
 
 main_01 group SLOWDOWN_TEXT, m_TEXT, EMS_TEXT, ma_TEXT, CFG_LRES_TEXT, mai_TEXT, main_TEXT, main__TEXT, PLAYFLD_TEXT, main_0_TEXT, HUD_OVRL_TEXT, DIALOG_TEXT, PLAYER_P_TEXT, main_01_TEXT
 g_SHARED group SHARED, SHARED_
-main_03 group SCROLLY3_TEXT, MOTION_3_TEXT, main_031_TEXT, BULLET_A_TEXT, main_032_TEXT, main_033_TEXT, MB_DFT_TEXT, LASER_SC_TEXT, CHEETO_U_TEXT, IT_SPL_U_TEXT, BULLET_U_TEXT, main_034_TEXT, main_035_TEXT, BOSS_6_TEXT, BOSS_X_TEXT, main_036_TEXT, BOSS_TEXT
+main_03 group SCROLLY3_TEXT, MOTION_3_TEXT, main_031_TEXT, BULLET_A_TEXT, main_032_TEXT, main_033_TEXT, MB_DFT_TEXT, LASER_SC_TEXT, CHEETO_U_TEXT, IT_SPL_U_TEXT, BULLET_U_TEXT, MIDBOSS1_TEXT, main_034_TEXT, main_035_TEXT, BOSS_6_TEXT, BOSS_X_TEXT, main_036_TEXT, BOSS_TEXT
 
 ; ===========================================================================
 
@@ -10402,45 +10402,12 @@ BULLET_U_TEXT	segment	byte public 'CODE' use16
 	extern @bullets_update$qv:proc
 BULLET_U_TEXT	ends
 
+MIDBOSS1_TEXT	segment	byte public 'CODE' use16
+	@midboss1_move$qv procdesc near
+MIDBOSS1_TEXT	ends
+
 main_034_TEXT	segment	byte public 'CODE' use16
 
-; =============== S U B	R O U T	I N E =======================================
-
-; Attributes: bp-based frame
-
-sub_17FC6	proc near
-		push	bp
-		mov	bp, sp
-		mov	ax, _midboss_pos.cur.x
-		mov	_midboss_pos.prev.x, ax
-		mov	ax, _midboss_pos.cur.y
-		mov	_midboss_pos.prev.y, ax
-		push	(192 shl 4)
-		push	_midboss_pos.velocity.x
-		mov	al, _midboss_angle
-		mov	ah, 0
-		add	ax, ax
-		mov	bx, ax
-		push	_CosTable8[bx]
-		call	vector1_at
-		mov	_midboss_pos.cur.x, ax
-		push	(96 shl 4)
-		push	_midboss_pos.velocity.x
-		mov	al, _midboss_angle
-		mov	ah, 0
-		add	ax, ax
-		mov	bx, ax
-		push	_SinTable8[bx]
-		call	vector1_at
-		mov	_midboss_pos.cur.y, ax
-		mov	al, _midboss_angle
-		add	al, -2
-		mov	_midboss_angle, al
-		pop	bp
-		retn
-sub_17FC6	endp
-
-
 ; =============== S U B	R O U T	I N E =======================================
 
 ; Attributes: bp-based frame
@@ -10559,7 +10526,7 @@ loc_1812B:
 		xor	edx, edx
 		div	ebx
 		mov	_midboss_pos.velocity.x, ax
-		call	sub_17FC6
+		call	@midboss1_move$qv
 		cmp	_midboss_phase_frame, 1500
 		jge	short loc_1818B
 		cmp	_midboss_hp, 0