diff --git a/UnleashedRecomp/CMakeLists.txt b/UnleashedRecomp/CMakeLists.txt
index 66b60a44..c7ba186f 100644
--- a/UnleashedRecomp/CMakeLists.txt
+++ b/UnleashedRecomp/CMakeLists.txt
@@ -183,6 +183,8 @@ set(UNLEASHED_RECOMP_USER_CXX_SOURCES
     "user/config.cpp"
     "user/registry.cpp"
     "user/paths.cpp"
+    "user/persistent_data.cpp"
+    "user/persistent_storage_manager.cpp"
 )
 
 set(UNLEASHED_RECOMP_MOD_CXX_SOURCES
diff --git a/UnleashedRecomp/api/SWA/System/ApplicationDocument.h b/UnleashedRecomp/api/SWA/System/ApplicationDocument.h
index 21949711..1e6ab27f 100644
--- a/UnleashedRecomp/api/SWA/System/ApplicationDocument.h
+++ b/UnleashedRecomp/api/SWA/System/ApplicationDocument.h
@@ -80,9 +80,13 @@ namespace SWA
             boost::shared_ptr<Hedgehog::Mirage::CRenderScene> m_spRenderScene;
             SWA_INSERT_PADDING(0x04);
             boost::shared_ptr<CGameParameter> m_spGameParameter;
-            SWA_INSERT_PADDING(0x78);
+            SWA_INSERT_PADDING(0x0C);
+            boost::anonymous_shared_ptr m_spItemParamManager;
+            SWA_INSERT_PADDING(0x64);
             boost::shared_ptr<Hedgehog::Base::CCriticalSection> m_spCriticalSection;
-            SWA_INSERT_PADDING(0x20);
+            SWA_INSERT_PADDING(0x14);
+            bool m_ShowDLCInfo;
+            SWA_INSERT_PADDING(0x08);
         };
 
         // TODO: Hedgehog::Base::TSynchronizedPtr<CApplicationDocument>
@@ -111,7 +115,9 @@ namespace SWA
     SWA_ASSERT_OFFSETOF(CApplicationDocument::CMember, m_Field10C, 0x10C);
     SWA_ASSERT_OFFSETOF(CApplicationDocument::CMember, m_spRenderScene, 0x12C);
     SWA_ASSERT_OFFSETOF(CApplicationDocument::CMember, m_spGameParameter, 0x138);
+    SWA_ASSERT_OFFSETOF(CApplicationDocument::CMember, m_spItemParamManager, 0x14C);
     SWA_ASSERT_OFFSETOF(CApplicationDocument::CMember, m_spCriticalSection, 0x1B8);
+    SWA_ASSERT_OFFSETOF(CApplicationDocument::CMember, m_ShowDLCInfo, 0x1D4);
     SWA_ASSERT_SIZEOF(CApplicationDocument::CMember, 0x1E0);
 
     SWA_ASSERT_OFFSETOF(CApplicationDocument, m_pMember, 0x04);
diff --git a/UnleashedRecomp/api/SWA/System/GameParameter.h b/UnleashedRecomp/api/SWA/System/GameParameter.h
index 95618144..da6b3735 100644
--- a/UnleashedRecomp/api/SWA/System/GameParameter.h
+++ b/UnleashedRecomp/api/SWA/System/GameParameter.h
@@ -7,11 +7,19 @@ namespace SWA
     class CGameParameter // : public Hedgehog::Universe::CMessageActor
     {
     public:
-        struct SSaveData;
+        struct SSaveData
+        {
+            SWA_INSERT_PADDING(0x8600);
+            be<uint32_t> DLCFlags[8];
+            SWA_INSERT_PADDING(0x15C);
+        };
+
         struct SStageParameter;
 
         SWA_INSERT_PADDING(0x94);
         xpointer<SSaveData> m_pSaveData;
         xpointer<SStageParameter> m_pStageParameter;
     };
+
+    SWA_ASSERT_OFFSETOF(CGameParameter::SSaveData, DLCFlags, 0x8600);
 }
diff --git a/UnleashedRecomp/main.cpp b/UnleashedRecomp/main.cpp
index a55c0181..ccf8b81c 100644
--- a/UnleashedRecomp/main.cpp
+++ b/UnleashedRecomp/main.cpp
@@ -13,6 +13,7 @@
 #include <hid/hid.h>
 #include <user/config.h>
 #include <user/paths.h>
+#include <user/persistent_storage_manager.h>
 #include <user/registry.h>
 #include <kernel/xdbf.h>
 #include <install/installer.h>
@@ -212,6 +213,7 @@ int main(int argc, char *argv[])
     }
 
     Config::Load();
+    PersistentStorageManager::LoadBinary();
 
 #if defined(_WIN32) && defined(UNLEASHED_RECOMP_D3D12)
     for (auto& dll : g_D3D12RequiredModules)
diff --git a/UnleashedRecomp/patches/misc_patches.cpp b/UnleashedRecomp/patches/misc_patches.cpp
index 9f318fb4..78d5e085 100644
--- a/UnleashedRecomp/patches/misc_patches.cpp
+++ b/UnleashedRecomp/patches/misc_patches.cpp
@@ -1,6 +1,7 @@
 #include <api/SWA.h>
 #include <ui/game_window.h>
 #include <user/achievement_manager.h>
+#include <user/persistent_storage_manager.h>
 #include <user/config.h>
 
 void AchievementManagerUnlockMidAsmHook(PPCRegister& id)
@@ -156,3 +157,23 @@ void DisableBoostFilterMidAsmHook(PPCRegister& r11)
             r11.u32 = 0;
     }
 }
+
+// DLC save data flag check.
+// 
+// The DLC checks are fundamentally broken in this game, resulting in this method always
+// returning true and displaying the DLC info message when it shouldn't be.
+// 
+// The original intent here seems to have been to display the message every time new DLC
+// content is installed, but the flags in the save data never get written to properly,
+// causing this function to always pass in some way.
+//
+// We bypass the save data completely and write to external persistent storage to store
+// whether we've seen the DLC info message instead. This way we can retain the original
+// broken game behaviour, whilst also providing a fix for this issue that is safe.
+PPC_FUNC_IMPL(__imp__sub_824EE620);
+PPC_FUNC(sub_824EE620)
+{
+    __imp__sub_824EE620(ctx, base);
+
+    ctx.r3.u32 = PersistentStorageManager::ShouldDisplayDLCMessage(true);
+}
diff --git a/UnleashedRecomp/patches/resident_patches.cpp b/UnleashedRecomp/patches/resident_patches.cpp
index 64a220d7..c421946c 100644
--- a/UnleashedRecomp/patches/resident_patches.cpp
+++ b/UnleashedRecomp/patches/resident_patches.cpp
@@ -2,11 +2,10 @@
 #include <hid/hid.h>
 #include <os/logger.h>
 #include <user/achievement_manager.h>
+#include <user/persistent_storage_manager.h>
 #include <user/config.h>
 #include <app.h>
 
-bool m_isSavedAchievementData = false;
-
 // SWA::Message::MsgRequestStartLoading::Impl
 PPC_FUNC_IMPL(__imp__sub_824DCF38);
 PPC_FUNC(sub_824DCF38)
@@ -99,20 +98,23 @@ PPC_FUNC(sub_824E5170)
 
     App::s_isSaving = pSaveIcon->m_IsVisible;
 
+    static bool isSavedExtraData = false;
+
     if (pSaveIcon->m_IsVisible)
     {
         App::s_isSaveDataCorrupt = false;
 
-        if (!m_isSavedAchievementData)
+        if (!isSavedExtraData)
         {
             AchievementManager::Save();
+            PersistentStorageManager::SaveBinary();
 
-            m_isSavedAchievementData = true;
+            isSavedExtraData = true;
         }
     }
     else
     {
-        m_isSavedAchievementData = false;
+        isSavedExtraData = false;
     }
 }
 
diff --git a/UnleashedRecomp/user/achievement_manager.h b/UnleashedRecomp/user/achievement_manager.h
index eab9c829..57317fd5 100644
--- a/UnleashedRecomp/user/achievement_manager.h
+++ b/UnleashedRecomp/user/achievement_manager.h
@@ -4,6 +4,7 @@
 
 enum class EAchStatus
 {
+    Unknown,
     Success,
     IOError,
     BadFileSize,
@@ -16,7 +17,7 @@ class AchievementManager
 {
 public:
     static inline AchievementData Data{};
-    static inline EAchStatus Status{};
+    static inline EAchStatus Status{ EAchStatus::Unknown };
 
     static std::filesystem::path GetDataPath(bool checkForMods)
     {
diff --git a/UnleashedRecomp/user/persistent_data.cpp b/UnleashedRecomp/user/persistent_data.cpp
new file mode 100644
index 00000000..1bdd75b8
--- /dev/null
+++ b/UnleashedRecomp/user/persistent_data.cpp
@@ -0,0 +1,18 @@
+#include "persistent_data.h"
+
+bool PersistentData::VerifySignature() const
+{
+    char sig[4] = EXT_SIGNATURE;
+
+    return memcmp(Header.Signature, sig, sizeof(Header.Signature)) == 0;
+}
+
+bool PersistentData::VerifyVersion() const
+{
+    return Header.Version == ExtVersion EXT_VERSION;
+}
+
+bool PersistentData::VerifyHeader() const
+{
+    return Header.HeaderSize == sizeof(ExtHeader);
+}
diff --git a/UnleashedRecomp/user/persistent_data.h b/UnleashedRecomp/user/persistent_data.h
new file mode 100644
index 00000000..5a8dd0ec
--- /dev/null
+++ b/UnleashedRecomp/user/persistent_data.h
@@ -0,0 +1,52 @@
+#pragma once
+
+#include <user/paths.h>
+
+#define EXT_FILENAME    "EXT-DATA"
+#define EXT_SIGNATURE   { 'E', 'X', 'T', ' ' }
+#define EXT_VERSION     { 1, 0, 0 }
+
+enum class EDLCFlag
+{
+    ApotosAndShamar,
+    Spagonia,
+    Chunnan,
+    Mazuri,
+    Holoska,
+    EmpireCityAndAdabat,
+    Count
+};
+
+class PersistentData
+{
+public:
+    struct ExtVersion
+    {
+        uint8_t Major;
+        uint8_t Minor;
+        uint8_t Revision;
+        uint8_t Reserved;
+
+        bool operator==(const ExtVersion& other) const
+        {
+            return Major == other.Major &&
+                   Minor == other.Minor &&
+                   Revision == other.Revision;
+        }
+    };
+
+    struct ExtHeader
+    {
+        char Signature[4] EXT_SIGNATURE;
+        ExtVersion Version EXT_VERSION;
+        uint32_t HeaderSize{ sizeof(ExtHeader) };
+        uint32_t Reserved;
+    };
+
+    ExtHeader Header;
+    bool DLCFlags[6];
+
+    bool VerifySignature() const;
+    bool VerifyVersion() const;
+    bool VerifyHeader() const;
+};
diff --git a/UnleashedRecomp/user/persistent_storage_manager.cpp b/UnleashedRecomp/user/persistent_storage_manager.cpp
new file mode 100644
index 00000000..8883ba6a
--- /dev/null
+++ b/UnleashedRecomp/user/persistent_storage_manager.cpp
@@ -0,0 +1,123 @@
+#include "persistent_storage_manager.h"
+#include <install/installer.h>
+#include <os/logger.h>
+#include <user/paths.h>
+
+bool PersistentStorageManager::ShouldDisplayDLCMessage(bool setOffendingDLCFlag)
+{
+    auto result = false;
+
+    if (BinStatus != EBinStatus::Success)
+        return result;
+
+    static std::unordered_map<EDLCFlag, DLC> flags =
+    {
+        { EDLCFlag::ApotosAndShamar, DLC::ApotosShamar },
+        { EDLCFlag::Spagonia, DLC::Spagonia },
+        { EDLCFlag::Chunnan, DLC::Chunnan },
+        { EDLCFlag::Mazuri, DLC::Mazuri },
+        { EDLCFlag::Holoska, DLC::Holoska },
+        { EDLCFlag::EmpireCityAndAdabat, DLC::EmpireCityAdabat }
+    };
+
+    for (auto& pair : flags)
+    {
+        if (!Data.DLCFlags[(int)pair.first] && Installer::checkDLCInstall(GetGamePath(), pair.second))
+        {
+            if (setOffendingDLCFlag)
+                Data.DLCFlags[(int)pair.first] = true;
+
+            result = true;
+        }
+    }
+
+    return result;
+}
+
+void PersistentStorageManager::LoadBinary()
+{
+    BinStatus = EBinStatus::Success;
+
+    auto dataPath = GetDataPath(true);
+
+    if (!std::filesystem::exists(dataPath))
+    {
+        // Try loading base persistent data as fallback.
+        dataPath = GetDataPath(false);
+
+        if (!std::filesystem::exists(dataPath))
+            return;
+    }
+
+    std::error_code ec;
+    auto fileSize = std::filesystem::file_size(dataPath, ec);
+    auto dataSize = sizeof(PersistentData);
+
+    if (fileSize != dataSize)
+    {
+        BinStatus = EBinStatus::BadFileSize;
+        return;
+    }
+
+    std::ifstream file(dataPath, std::ios::binary);
+
+    if (!file)
+    {
+        BinStatus = EBinStatus::IOError;
+        return;
+    }
+
+    PersistentData data{};
+
+    file.read((char*)&data.Header.Signature, sizeof(data.Header.Signature));
+
+    if (!data.VerifySignature())
+    {
+        BinStatus = EBinStatus::BadSignature;
+        file.close();
+        return;
+    }
+
+    file.read((char*)&data.Header.Version, sizeof(data.Header.Version));
+
+    // TODO: upgrade in future if the version changes.
+    if (!data.VerifyVersion())
+    {
+        BinStatus = EBinStatus::BadVersion;
+        file.close();
+        return;
+    }
+
+    file.read((char*)&data.Header.HeaderSize, sizeof(data.Header.HeaderSize));
+
+    if (!data.VerifyHeader())
+    {
+        BinStatus = EBinStatus::BadHeader;
+        file.close();
+        return;
+    }
+
+    file.seekg(0);
+    file.read((char*)&data, sizeof(data));
+    file.close();
+
+    memcpy(&Data, &data, dataSize);
+}
+
+void PersistentStorageManager::SaveBinary()
+{
+    LOGN("Saving persistent storage binary...");
+
+    std::ofstream file(GetDataPath(true), std::ios::binary);
+
+    if (!file)
+    {
+        LOGN_ERROR("Failed to write persistent storage binary.");
+        return;
+    }
+
+    file.write((const char*)&Data, sizeof(PersistentData));
+    file.close();
+
+    BinStatus = EBinStatus::Success;
+}
diff --git a/UnleashedRecomp/user/persistent_storage_manager.h b/UnleashedRecomp/user/persistent_storage_manager.h
new file mode 100644
index 00000000..d75d24ae
--- /dev/null
+++ b/UnleashedRecomp/user/persistent_storage_manager.h
@@ -0,0 +1,30 @@
+#pragma once
+
+#include <user/persistent_data.h>
+
+enum class EBinStatus
+{
+    Unknown,
+    Success,
+    IOError,
+    BadFileSize,
+    BadSignature,
+    BadVersion,
+    BadHeader
+};
+
+class PersistentStorageManager
+{
+public:
+    static inline PersistentData Data{};
+    static inline EBinStatus BinStatus{ EBinStatus::Unknown };
+
+    static std::filesystem::path GetDataPath(bool checkForMods)
+    {
+        return GetSavePath(checkForMods) / EXT_FILENAME;
+    }
+
+    static bool ShouldDisplayDLCMessage(bool setOffendingDLCFlag);
+    static void LoadBinary();
+    static void SaveBinary();
+};