After you

asm/macros/battle_script.inc

@@ -1440,6 +1440,11 @@
 	.4byte \ptr
 	.endm
 	
+	.macro tryafteryou ptr
+	various BS_ATTACKER, VARIOUS_AFTER_YOU
+	.4byte \ptr
+	.endm
+	
 	.macro invertstatstages battler
 	various \battler, VARIOUS_INVERT_STAT_STAGES
 	.endm

data/battle_scripts_1.s

@@ -324,6 +324,19 @@ gBattleScriptsForMoveEffects:: @ 82D86A8
 	.4byte BattleScript_EffectPsychoShift
 	.4byte BattleScript_EffectPowerTrick
 	.4byte BattleScript_EffectFlameBurst
+	.4byte BattleScript_EffectAfterYou
+	
+BattleScript_EffectAfterYou:
+	attackcanceler
+	accuracycheck BattleScript_PrintMoveMissed, ACC_CURR_MOVE
+	attackstring
+	ppreduce
+	tryafteryou BattleScript_ButItFailed
+	attackanimation
+	waitanimation
+	printstring STRINGID_KINDOFFER
+	waitmessage 0x40
+	goto BattleScript_MoveEnd
 	
 BattleScript_EffectFlameBurst:
 	setmoveeffect MOVE_EFFECT_FLAME_BURST | MOVE_EFFECT_AFFECTS_USER

include/constants/battle_move_effects.h

@@ -313,5 +313,6 @@
 #define EFFECT_PSYCHO_SHIFT 307
 #define EFFECT_POWER_TRICK 308
 #define EFFECT_FLAME_BURST 309
+#define EFFECT_AFTER_YOU 310
 
 #endif  // GUARD_CONSTANTS_BATTLE_MOVE_EFFECTS_H

include/constants/battle_script_commands.h

@@ -115,6 +115,7 @@
 #define VARIOUS_PSYCHO_SHIFT					61
 #define VARIOUS_CURE_STATUS						62
 #define VARIOUS_POWER_TRICK						63
+#define VARIOUS_AFTER_YOU						64
 
 // atk80, dmg manipulation
 #define ATK80_DMG_CHANGE_SIGN                               0

src/battle_script_commands.c

@@ -6980,6 +6980,36 @@ static void atk76_various(void)
         gStatuses3[gActiveBattler] ^= STATUS3_POWER_TRICK;
         SWAP(gBattleMons[gActiveBattler].attack, gBattleMons[gActiveBattler].defense, i);
         break;
+    case VARIOUS_AFTER_YOU:
+        if (GetBattlerTurnOrderNum(gBattlerAttacker) > GetBattlerTurnOrderNum(gBattlerTarget)
+            || GetBattlerTurnOrderNum(gBattlerAttacker) == GetBattlerTurnOrderNum(gBattlerTarget) + 1)
+        {
+            gBattlescriptCurrInstr = T1_READ_PTR(gBattlescriptCurrInstr + 3);
+        }
+        else
+        {
+            for (i = 0; i < gBattlersCount; i++)
+                data[i] = gBattlerByTurnOrder[i];
+            if (GetBattlerTurnOrderNum(gBattlerAttacker) == 0 && GetBattlerTurnOrderNum(gBattlerTarget) == 2)
+            {
+                gBattlerByTurnOrder[1] = gBattlerTarget;
+                gBattlerByTurnOrder[2] = data[1];
+                gBattlerByTurnOrder[3] = data[3];
+            }
+            else if (GetBattlerTurnOrderNum(gBattlerAttacker) == 0 && GetBattlerTurnOrderNum(gBattlerTarget) == 3)
+            {
+                gBattlerByTurnOrder[1] = gBattlerTarget;
+                gBattlerByTurnOrder[2] = data[1];
+                gBattlerByTurnOrder[3] = data[2];
+            }
+            else
+            {
+                gBattlerByTurnOrder[2] = gBattlerTarget;
+                gBattlerByTurnOrder[3] = data[2];
+            }
+            gBattlescriptCurrInstr += 7;
+        }
+        return;
     }
 
     gBattlescriptCurrInstr += 3;

src/data/battle_moves.h

@@ -5949,7 +5949,7 @@ const struct BattleMove gBattleMoves[MOVES_COUNT] =
 		.split = SPLIT_STATUS,
 	},
 	{ // MOVE_AFTER_YOU
-		.effect = EFFECT_PLACEHOLDER, // Needs a custom move effect
+		.effect = EFFECT_AFTER_YOU,
 		.power = 0,
 		.type = TYPE_NORMAL,
 		.accuracy = 0,