diff --git a/src/phases.ts b/src/phases.ts
index 271e5350c82..6cc6af93ef9 100644
--- a/src/phases.ts
+++ b/src/phases.ts
@@ -775,7 +775,7 @@ export class EncounterPhase extends BattlePhase {
 
       this.scene.ui.setMode(Mode.MESSAGE).then(() => {
         if (!this.loaded) {
-          this.scene.gameData.saveAll(this.scene, true).then(success => {
+          this.scene.gameData.saveAll(this.scene, true, battle.waveIndex % 5 === 1).then(success => {
             this.scene.disableMenu = false;
             if (!success)
               return this.scene.reset(true);
diff --git a/src/system/game-data.ts b/src/system/game-data.ts
index 7f6e1475b4a..90722d1ce37 100644
--- a/src/system/game-data.ts
+++ b/src/system/game-data.ts
@@ -277,7 +277,7 @@ export class GameData {
       const maxIntAttrValue = Math.pow(2, 31);
       const systemData = JSON.stringify(data, (k: any, v: any) => typeof v === 'bigint' ? v <= maxIntAttrValue ? Number(v) : v.toString() : v);
 
-      if (!bypassLogin) {
+      if (!bypassLogin && !localStorage.getItem('data')) {
         Utils.apiPost(`savedata/update?datatype=${GameDataType.SYSTEM}`, systemData, undefined, true)
           .then(response => response.text())
           .then(error => {
@@ -293,12 +293,15 @@ export class GameData {
               console.error(error);
               return resolve(false);
             }
+            localStorage.removeItem('data');
             resolve(true);
           });
       } else {
-        localStorage.setItem('data_bak', localStorage.getItem('data'));
+        const encFunc = bypassLogin
+          ? (data: string) => btoa(data)
+          : (data: string) => AES.encrypt(data, saveKey);
 
-        localStorage.setItem('data', btoa(systemData));
+        localStorage.setItem('data', encFunc(systemData));
 
         this.scene.ui.savingIcon.hide();
 
@@ -309,7 +312,7 @@ export class GameData {
 
   public loadSystem(): Promise<boolean> {
     return new Promise<boolean>(resolve => {
-      if (bypassLogin && !localStorage.hasOwnProperty('data'))
+      if (bypassLogin && !localStorage.getItem('data'))
         return resolve(false);
 
       const handleSystemData = (systemDataStr: string) => {
@@ -421,7 +424,7 @@ export class GameData {
         }
       }
 
-      if (!bypassLogin) {
+      if (!bypassLogin && !localStorage.getItem('data')) {
         Utils.apiFetch(`savedata/get?datatype=${GameDataType.SYSTEM}`, true)
           .then(response => response.text())
           .then(response => {
@@ -439,8 +442,12 @@ export class GameData {
 
             handleSystemData(response);
           });
-      } else
-        handleSystemData(atob(localStorage.getItem('data')));
+      } else {
+        const decFunc = bypassLogin
+          ? (data: string) => atob(data)
+          : (data: string) => AES.decrypt(data, saveKey).toString(enc.Utf8);
+        handleSystemData(decFunc(localStorage.getItem('data')));
+      }
     });
   }
 
@@ -557,40 +564,6 @@ export class GameData {
     } as SessionSaveData;
   }
 
-  saveSession(scene: BattleScene, skipVerification?: boolean): Promise<boolean> {
-    return new Promise<boolean>(resolve => {
-      Utils.executeIf(!skipVerification, updateUserInfo).then(success => {
-        if (success !== null && !success)
-          return resolve(false);
-
-        const sessionData = this.getSessionSaveData(scene);
-
-        if (!bypassLogin) {
-          Utils.apiPost(`savedata/update?datatype=${GameDataType.SESSION}&slot=${scene.sessionSlotId}&trainerId=${this.trainerId}&secretId=${this.secretId}`, JSON.stringify(sessionData), undefined, true)
-            .then(response => response.text())
-            .then(error => {
-              if (error) {
-                if (error.startsWith('session out of date')) {
-                  this.scene.clearPhaseQueue();
-                  this.scene.unshiftPhase(new ReloadSessionPhase(this.scene));
-                }
-                console.error(error);
-                return resolve(false);
-              }
-              console.debug('Session data saved');
-              resolve(true);
-            });
-        } else {
-          localStorage.setItem(`sessionData${scene.sessionSlotId ? scene.sessionSlotId : ''}`, btoa(JSON.stringify(sessionData)));
-
-          console.debug('Session data saved');
-
-          resolve(true);
-        }
-      });
-    });
-  }
-
   getSession(slotId: integer): Promise<SessionSaveData> {
     return new Promise(async (resolve, reject) => {
       if (slotId < 0)
@@ -605,7 +578,7 @@ export class GameData {
         }
       };
 
-      if (!bypassLogin) {
+      if (!bypassLogin && !localStorage.getItem(`sessionData${slotId ? slotId : ''}`)) {
         Utils.apiFetch(`savedata/get?datatype=${GameDataType.SESSION}&slot=${slotId}`, true)
           .then(response => response.text())
           .then(async response => {
@@ -618,9 +591,12 @@ export class GameData {
           });
       } else {
         const sessionData = localStorage.getItem(`sessionData${slotId ? slotId : ''}`);
-        if (sessionData)
-          await handleSessionData(atob(sessionData));
-        else
+        if (sessionData) {
+          const decFunc = bypassLogin
+            ? (data: string) => atob(data)
+            : (data: string) => AES.decrypt(data, saveKey).toString(enc.Utf8);
+          await handleSessionData(decFunc(sessionData));
+        } else
           return resolve(null);
       }
     });
@@ -731,7 +707,7 @@ export class GameData {
   deleteSession(slotId: integer): Promise<boolean> {
     return new Promise<boolean>(resolve => {
       if (bypassLogin) {
-        localStorage.removeItem('sessionData');
+        localStorage.removeItem(`sessionData${this.scene.sessionSlotId ? this.scene.sessionSlotId : ''}`);
         return resolve(true);
       }
 
@@ -741,6 +717,7 @@ export class GameData {
         Utils.apiFetch(`savedata/delete?datatype=${GameDataType.SESSION}&slot=${slotId}`, true).then(response => {
           if (response.ok) {
             loggedInUser.lastSessionSlot = -1;
+            localStorage.removeItem(`sessionData${this.scene.sessionSlotId ? this.scene.sessionSlotId : ''}`);
             resolve(true);
           }
           return response.text();
@@ -771,8 +748,10 @@ export class GameData {
           return resolve([false, false]);
         const sessionData = this.getSessionSaveData(scene);
         Utils.apiPost(`savedata/clear?slot=${slotId}&trainerId=${this.trainerId}&secretId=${this.secretId}`, JSON.stringify(sessionData), undefined, true).then(response => {
-          if (response.ok)
+          if (response.ok) {
             loggedInUser.lastSessionSlot = -1;
+            localStorage.removeItem(`sessionData${this.scene.sessionSlotId ? this.scene.sessionSlotId : ''}`);
+          }
           return response.json();
         }).then(jsonResponse => {
           if (!jsonResponse.error)
@@ -825,13 +804,12 @@ export class GameData {
     }) as SessionSaveData;
   }
 
-  saveAll(scene: BattleScene, skipVerification?: boolean): Promise<boolean> {
+  saveAll(scene: BattleScene, skipVerification: boolean = false, sync: boolean = false): Promise<boolean> {
     return new Promise<boolean>(resolve => {
       Utils.executeIf(!skipVerification, updateUserInfo).then(success => {
         if (success !== null && !success)
           return resolve(false);
         this.scene.ui.savingIcon.show();
-        const data = this.getSystemSaveData();
         const sessionData = this.getSessionSaveData(scene);
 
         const maxIntAttrValue = Math.pow(2, 31);
@@ -843,7 +821,7 @@ export class GameData {
           sessionSlotId: scene.sessionSlotId
         };
 
-        if (!bypassLogin) {
+        if (!bypassLogin && sync) {
           Utils.apiPost('savedata/updateall', JSON.stringify(request, (k: any, v: any) => typeof v === 'bigint' ? v <= maxIntAttrValue ? Number(v) : v.toString() : v), undefined, true)
             .then(response => response.text())
             .then(error => {
@@ -859,14 +837,18 @@ export class GameData {
                 console.error(error);
                 return resolve(false);
               }
+              localStorage.removeItem('data');
+              localStorage.removeItem(`sessionData${scene.sessionSlotId ? scene.sessionSlotId : ''}`);
               resolve(true);
             });
         } else {
-          localStorage.setItem('data_bak', localStorage.getItem('data'));
+          const encFunc = bypassLogin
+            ? (data: string) => btoa(data)
+            : (data: string) => AES.encrypt(data, saveKey);
 
-          localStorage.setItem('data', btoa(JSON.stringify(systemData, (k: any, v: any) => typeof v === 'bigint' ? v <= maxIntAttrValue ? Number(v) : v.toString() : v)));
+          localStorage.setItem('data', encFunc(JSON.stringify(systemData, (k: any, v: any) => typeof v === 'bigint' ? v <= maxIntAttrValue ? Number(v) : v.toString() : v)));
 
-          localStorage.setItem(`sessionData${scene.sessionSlotId ? scene.sessionSlotId : ''}`, btoa(JSON.stringify(sessionData)));
+          localStorage.setItem(`sessionData${scene.sessionSlotId ? scene.sessionSlotId : ''}`, encFunc(JSON.stringify(sessionData)));
 
           console.debug('Session data saved');
 
@@ -910,8 +892,12 @@ export class GameData {
           });
       } else {
         const data = localStorage.getItem(dataKey);
-        if (data)
-          handleData(atob(data));
+        if (data) {
+          const decFunc = bypassLogin
+            ? (data: string) => atob(data)
+            : (data: string) => AES.decrypt(data, saveKey).toString(enc.Utf8);
+          handleData(decFunc(data));
+        }
         resolve(!!data);
       }
     });
@@ -979,7 +965,7 @@ export class GameData {
                 return this.scene.ui.showText(`Your ${dataName} data could not be loaded. It may be corrupted.`, null, () => this.scene.ui.showText(null, 0), Utils.fixedInt(1500));
               this.scene.ui.showText(`Your ${dataName} data will be overridden and the page will reload. Proceed?`, null, () => {
                 this.scene.ui.setOverlayMode(Mode.CONFIRM, () => {
-                  if (!bypassLogin && dataType < GameDataType.SETTINGS) {
+                  if (!bypassLogin && dataType < GameDataType.SETTINGS && localStorage.getItem(dataKey)) {
                     updateUserInfo().then(success => {
                       if (!success)
                         return displayError(`Could not contact the server. Your ${dataName} data could not be imported.`);
@@ -990,11 +976,15 @@ export class GameData {
                             console.error(error);
                             return displayError(`An error occurred while updating ${dataName} data. Please contact the administrator.`);
                           }
+                          localStorage.removeItem(dataKey);
                           window.location = window.location;
                         });
                     });
                   } else {
-                    localStorage.setItem(dataKey, btoa(dataStr));
+                    const encFunc = bypassLogin || dataType === GameDataType.SETTINGS
+                      ? (data: string) => btoa(data)
+                      : (data: string) => AES.encrypt(data, saveKey);
+                    localStorage.setItem(dataKey, encFunc(dataStr));
                     window.location = window.location;
                   }
                 }, () => {