diff --git a/src/battle-scene.ts b/src/battle-scene.ts
index 27166347039..12d7d5d1d 100644
--- a/src/battle-scene.ts
+++ b/src/battle-scene.ts
@@ -1558,6 +1558,7 @@ export default class BattleScene extends SceneBase {
 			const soundName = modifier.type.soundName;
 			this.validateAchvs(ModifierAchv, modifier);
 			const modifiersToRemove: PersistentModifier[] = [];
+			const modifierPromises: Promise<boolean>[] = [];
 			if (modifier instanceof PersistentModifier) {
 				if (modifier instanceof TerastallizeModifier)
 					modifiersToRemove.push(...(this.findModifiers(m => m instanceof TerastallizeModifier && m.pokemonId === modifier.pokemonId)));
@@ -1596,11 +1597,14 @@ export default class BattleScene extends SceneBase {
 						} else if (modifier instanceof FusePokemonModifier)
 							args.push(this.getPokemonById(modifier.fusePokemonId) as PlayerPokemon);
 							
-						if (modifier.shouldApply(args))
-							modifier.apply(args);
+						if (modifier.shouldApply(args)) {
+							const result = modifier.apply(args);
+							if (result instanceof Promise)
+								modifierPromises.push(result);
+						}
 					}
 					
-					return Promise.allSettled(this.party.map(p => p.updateInfo(instant))).then(() => resolve());
+					return Promise.allSettled([this.party.map(p => p.updateInfo(instant)), ...modifierPromises]).then(() => resolve());
 				} else {
 					const args = [ this ];
 					if (modifier.shouldApply(args))
diff --git a/src/field/pokemon.ts b/src/field/pokemon.ts
index 06ff004b1..9dc560d80 100644
--- a/src/field/pokemon.ts
+++ b/src/field/pokemon.ts
@@ -601,8 +601,10 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
     return this.getMaxHp() - this.hp;
   }
 
-  getHpRatio(): number {
-    return Math.floor((this.hp / this.getMaxHp()) * 100) / 100;
+  getHpRatio(precise: boolean = false): number {
+    return precise
+      ? this.hp / this.getMaxHp()
+      : ((this.hp / this.getMaxHp()) * 100) / 100;
   }
 
   generateGender(): void {
@@ -2324,7 +2326,6 @@ export class PlayerPokemon extends Pokemon {
       let partyMemberIndex = this.scene.getParty().indexOf(this);
       if (partyMemberIndex > fusedPartyMemberIndex)
         partyMemberIndex--;
-      pokemon.getMoveset(true).map(m => this.scene.unshiftPhase(new LearnMovePhase(this.scene, partyMemberIndex, m.getMove().id)));
       const fusedPartyMemberHeldModifiers = this.scene.findModifiers(m => m instanceof PokemonHeldItemModifier
         && (m as PokemonHeldItemModifier).pokemonId === pokemon.id, true) as PokemonHeldItemModifier[];
       const transferModifiers: Promise<boolean>[] = [];
@@ -2334,6 +2335,8 @@ export class PlayerPokemon extends Pokemon {
         this.scene.updateModifiers(true, true).then(() => {
           this.scene.removePartyMemberModifiers(fusedPartyMemberIndex);
           this.scene.getParty().splice(fusedPartyMemberIndex, 1)[0];
+          const newPartyMemberIndex = this.scene.getParty().indexOf(this);
+          pokemon.getMoveset(true).map(m => this.scene.unshiftPhase(new LearnMovePhase(this.scene, newPartyMemberIndex, m.getMove().id)));
           pokemon.destroy();
           this.updateFusionPalette();
           resolve();
diff --git a/src/modifier/modifier.ts b/src/modifier/modifier.ts
index 115273db7..de4477a3e 100644
--- a/src/modifier/modifier.ts
+++ b/src/modifier/modifier.ts
@@ -109,7 +109,7 @@ export abstract class Modifier {
     return true;
   }
 
-  abstract apply(args: any[]): boolean;
+  abstract apply(args: any[]): boolean | Promise<boolean>;
 }
 
 export abstract class PersistentModifier extends Modifier {
@@ -1203,10 +1203,10 @@ export class FusePokemonModifier extends ConsumablePokemonModifier {
     return super.shouldApply(args) && args[1] instanceof PlayerPokemon && this.fusePokemonId === (args[1] as PlayerPokemon).id;
   }
 
-  apply(args: any[]): boolean {
-    (args[0] as PlayerPokemon).fuse(args[1] as PlayerPokemon);
-
-    return true;
+  apply(args: any[]): Promise<boolean> {
+    return new Promise<boolean>(resolve => {
+      (args[0] as PlayerPokemon).fuse(args[1] as PlayerPokemon).then(() => resolve(true));
+    });
   }
 }
 
diff --git a/src/phases.ts b/src/phases.ts
index ccc9318f8..015c487f5 100644
--- a/src/phases.ts
+++ b/src/phases.ts
@@ -4102,16 +4102,22 @@ export class SelectModifierPhase extends BattlePhase {
       }
 
       const applyModifier = (modifier: Modifier, playSound: boolean = false) => {
-        this.scene.addModifier(modifier, false, playSound);
+        const result = this.scene.addModifier(modifier, false, playSound);
         if (cost) {
           this.scene.money -= cost;
           this.scene.updateMoneyText();
           this.scene.playSound('buy');
           (this.scene.ui.getHandler() as ModifierSelectUiHandler).updateCostText();
         } else {
-          this.scene.ui.clearText();
-          this.scene.ui.setMode(Mode.MESSAGE);
-          super.end();
+          const doEnd = () => {
+            this.scene.ui.clearText();
+            this.scene.ui.setMode(Mode.MESSAGE);
+            super.end();
+          };
+          if (result instanceof Promise)
+            result.then(() => doEnd());
+          else
+            doEnd();
         }
       };
 
diff --git a/src/ui/battle-info.ts b/src/ui/battle-info.ts
index ce6c101f1..71f048310 100644
--- a/src/ui/battle-info.ts
+++ b/src/ui/battle-info.ts
@@ -193,7 +193,7 @@ export default class BattleInfo extends Phaser.GameObjects.Container {
         this.updateBossSegmentDividers(pokemon as EnemyPokemon);
     }
 
-    this.hpBar.setScale(pokemon.getHpRatio(), 1);
+    this.hpBar.setScale(pokemon.getHpRatio(true), 1);
     this.lastHpFrame = this.hpBar.scaleX > 0.5 ? 'high' : this.hpBar.scaleX > 0.25 ? 'medium' : 'low';
     this.hpBar.setFrame(this.lastHpFrame);
     if (this.player)
@@ -356,7 +356,7 @@ export default class BattleInfo extends Phaser.GameObjects.Container {
         this.scene.tweens.add({
           targets: this.hpBar,
           ease: 'Sine.easeOut',
-          scaleX: pokemon.getHpRatio(),
+          scaleX: pokemon.getHpRatio(true),
           duration: duration,
           onUpdate: () => {
             if (this.player && this.lastHp !== pokemon.hp) {