diff --git a/asm/pokenav.s b/asm/pokenav.s
index e2fb45851f..b89ea22baa 100644
--- a/asm/pokenav.s
+++ b/asm/pokenav.s
@@ -5,179 +5,6 @@
 
 	.text
 
-	thumb_func_start sub_81C87F0
-sub_81C87F0: @ 81C87F0
-	push {r4,lr}
-	movs r0, 0x11
-	bl GetSubstructPtr
-	adds r4, r0, 0
-	ldr r0, =0x0000089c
-	adds r1, r4, r0
-	movs r0, 0
-	str r0, [r1]
-	ldr r0, =sub_81C8A28
-	movs r1, 0x6
-	bl sub_81C7078
-	movs r1, 0x8A
-	lsls r1, 4
-	adds r4, r1
-	str r0, [r4]
-	pop {r4}
-	pop {r0}
-	bx r0
-	.pool
-	thumb_func_end sub_81C87F0
-
-	thumb_func_start sub_81C8820
-sub_81C8820: @ 81C8820
-	push {lr}
-	movs r0, 0x11
-	bl GetSubstructPtr
-	movs r1, 0x8A
-	lsls r1, 4
-	adds r0, r1
-	ldr r0, [r0]
-	bl sub_81C70D8
-	pop {r1}
-	bx r1
-	thumb_func_end sub_81C8820
-
-	thumb_func_start sub_81C8838
-sub_81C8838: @ 81C8838
-	push {r4,lr}
-	movs r0, 0x11
-	bl GetSubstructPtr
-	adds r4, r0, 0
-	ldr r0, =0x00000888
-	adds r2, r4, r0
-	ldrh r0, [r4, 0x8]
-	ldrh r1, [r2]
-	ldrh r3, [r2, 0x6]
-	adds r1, r3
-	ldrh r2, [r4, 0xA]
-	adds r2, r3
-	movs r3, 0xF
-	ands r2, r3
-	ldr r3, [r4, 0x38]
-	bl _call_via_r3
-	ldrb r0, [r4, 0x8]
-	movs r1, 0x1
-	bl CopyWindowToVram
-	pop {r4}
-	pop {r0}
-	bx r0
-	.pool
-	thumb_func_end sub_81C8838
-
-	thumb_func_start sub_81C8870
-sub_81C8870: @ 81C8870
-	push {r4,r5,lr}
-	adds r5, r0, 0
-	movs r0, 0x11
-	bl GetSubstructPtr
-	adds r4, r0, 0
-	cmp r5, 0x4
-	bhi _081C894C
-	lsls r0, r5, 2
-	ldr r1, =_081C8890
-	adds r0, r1
-	ldr r0, [r0]
-	mov pc, r0
-	.pool
-	.align 2, 0
-_081C8890:
-	.4byte _081C88A4
-	.4byte _081C88AC
-	.4byte _081C88D8
-	.4byte _081C8918
-	.4byte _081C8938
-_081C88A4:
-	adds r0, r4, 0
-	movs r1, 0x1
-	bl sub_81C9008
-_081C88AC:
-	ldr r0, =0x0000089c
-	adds r5, r4, r0
-	ldr r1, =0x0000088e
-	adds r0, r4, r1
-	ldr r1, [r5]
-	ldrh r0, [r0]
-	cmp r1, r0
-	beq _081C88C4
-	adds r0, r4, 0
-	movs r2, 0x1
-	bl sub_81C8B70
-_081C88C4:
-	ldr r0, [r5]
-	adds r0, 0x1
-	str r0, [r5]
-_081C88CA:
-	movs r0, 0
-	b _081C894E
-	.pool
-_081C88D8:
-	bl IsDma3ManagerBusyWithBgCopy
-	lsls r0, 24
-	cmp r0, 0
-	bne _081C8942
-	ldr r2, =0x0000089c
-	adds r0, r4, r2
-	subs r2, 0xC
-	adds r1, r4, r2
-	ldr r3, [r0]
-	ldrh r1, [r1]
-	cmp r3, r1
-	beq _081C88FC
-	movs r0, 0x6
-	b _081C894E
-	.pool
-_081C88FC:
-	ldr r0, =0x0000088e
-	adds r1, r4, r0
-	ldrh r0, [r1]
-	cmp r0, 0
-	beq _081C88CA
-	adds r2, r0, 0
-	adds r0, r4, 0
-	adds r1, r3, 0
-	bl sub_81C8B70
-	b _081C88CA
-	.pool
-_081C8918:
-	bl IsDma3ManagerBusyWithBgCopy
-	lsls r0, 24
-	cmp r0, 0
-	bne _081C8942
-	ldr r2, =0x0000088e
-	adds r1, r4, r2
-	ldrh r0, [r1]
-	cmp r0, 0
-	beq _081C894C
-	movs r1, 0
-	bl sub_81C84E8
-	b _081C88CA
-	.pool
-_081C8938:
-	bl sub_81C8630
-	adds r1, r0, 0
-	cmp r1, 0
-	beq _081C8946
-_081C8942:
-	movs r0, 0x2
-	b _081C894E
-_081C8946:
-	ldr r2, =0x0000088e
-	adds r0, r4, r2
-	strh r1, [r0]
-_081C894C:
-	movs r0, 0x4
-_081C894E:
-	pop {r4,r5}
-	pop {r1}
-	bx r1
-	.pool
-	thumb_func_end sub_81C8870
-
 	thumb_func_start sub_81C8958
 sub_81C8958: @ 81C8958
 	push {r4,r5,lr}
diff --git a/src/pokenav.c b/src/pokenav.c
index 1912e7e571..6e7049ddf9 100644
--- a/src/pokenav.c
+++ b/src/pokenav.c
@@ -36,8 +36,7 @@ struct UnknownSubSubStruct_0203CF40 {
     u8 unk4;
     u8 unk5;
     u16 unk6;
-    u8 windowId;
-    u8 unk9;
+    u16 windowId;
     u16 unkA;
     u16 unkC;
     u16 unkE;
@@ -173,18 +172,21 @@ extern u32 sub_81C91AC(struct UnknownSubStruct_81C81D4 *a0, const void *a1, void
 extern u32 sub_81C9160(struct UnknownSubSubStruct_81C81D4 *a0, void *a1);
 extern void sub_81C8ED0(void);
 extern void sub_81C8EF8(struct UnknownSubSubStruct_81C81D4 *a0, struct UnknownSubSubStruct_0203CF40 *a1);
-extern u32 sub_81C8870(s32 a0);
 extern u32 sub_81C8958(s32 a0);
+extern u32 sub_81C8A28(s32 a0);
+extern void sub_81C8B70(struct UnknownSubSubStruct_0203CF40 *a0, u32 a1, u32 a2);
+extern void sub_81C9008(struct UnknownSubStruct_81C81D4 *a0, u32 a1);
 
-u32 sub_81C85A0(s32);
+u32 sub_81C8870(s32 a0);
+u32 sub_81C85A0(s32 a0);
 void sub_81C8568(s32 a0, struct UnknownSubStruct_81C81D4 *a1);
-u32 sub_81C83F0(s32);
+u32 sub_81C83F0(s32 a0);
 bool32 sub_81C83E0(void);
 void sub_81C83AC(u32 a0, u32 a1, u32 a2, u32 a3, u32 a4, struct UnknownSubStruct_81C81D4 *a5);
 void sub_81C837C(struct UnknownSubSubStruct_81C81D4 *a0, struct UnknownSubStruct_81C81D4 *a1);
 void sub_81C835C(struct UnknownSubSubStruct_0203CF40 *a0);
 void sub_81C82E4(struct UnknownSubStruct_81C81D4 *a0);
-u32 sub_81C8254(s32);
+u32 sub_81C8254(s32 a0);
 u32 sub_81C791C(s32 a0);
 bool32 sub_81C756C(u32 a0);
 bool32 sub_81C76C4(void);
@@ -2027,4 +2029,83 @@ void sub_81C87AC(u16 a0)
     structPtr->unk888.unk0 = temp;
     structPtr->unk89C = 0;
     structPtr->unk8A0 = sub_81C7078(sub_81C8958, 6);
+}
+
+void sub_81C87F0(void)
+{
+    struct UnknownSubStruct_81C81D4 *structPtr;
+    structPtr = GetSubstructPtr(0x11);
+    structPtr->unk89C = 0;
+    structPtr->unk8A0 = sub_81C7078(sub_81C8A28, 6);
+}
+
+bool32 sub_81C8820(void)
+{
+    struct UnknownSubStruct_81C81D4 *structPtr;
+    structPtr = GetSubstructPtr(0x11);
+    return sub_81C70D8(structPtr->unk8A0);
+}
+
+void sub_81C8838(void)
+{
+    struct UnknownSubStruct_81C81D4 *structPtr;
+    struct UnknownSubSubStruct_81C81D4 *subStr;
+    structPtr = GetSubstructPtr(0x11);
+    subStr = &structPtr->unk888;
+    structPtr->unk38(structPtr->unk0.windowId, subStr->unk0 + subStr->unk6, (structPtr->unk0.unkA + subStr->unk6) & 0xF);
+    CopyWindowToVram(structPtr->unk0.windowId, 1);
+}
+
+u32 sub_81C8870(s32 a0)
+{
+    struct UnknownSubStruct_81C81D4 *structPtr;
+    u16 v1;
+    u32 v2;
+
+    // Needed to fix a register renaming issue.
+    register u16* temp asm("r1");
+    structPtr = GetSubstructPtr(0x11);
+
+    switch (a0)
+    {
+    case 0:
+        sub_81C9008(structPtr, 1);
+        // fall-through
+    case 1:
+        if (structPtr->unk89C != structPtr->unk888.unk6)
+            sub_81C8B70(&structPtr->unk0, structPtr->unk89C, 1);
+        
+        structPtr->unk89C++;
+        return 0;
+    case 2:
+        if (IsDma3ManagerBusyWithBgCopy())
+            return 2;
+        
+        if (structPtr->unk89C != structPtr->unk888.unk8)
+            return 6;
+        
+        if (structPtr->unk888.unk6 != 0)
+            sub_81C8B70(&structPtr->unk0, structPtr->unk89C, structPtr->unk888.unk6);
+        
+        return 0;
+    case 3:
+        if (IsDma3ManagerBusyWithBgCopy())
+            return 2;
+        temp = &structPtr->unk888.unk6;
+        v1 = *temp;
+        if (v1 == 0)
+            return 4;
+        
+        sub_81C84E8(v1, 0);
+        return 0;
+    case 4:
+         v2 = sub_81C8630();
+         if (v2)
+            return 2;
+
+        structPtr->unk888.unk6 = v2;
+        return 4;
+    default:
+        return 4;
+    }
 }
\ No newline at end of file