diff --git a/src/common/uuid.cpp b/src/common/uuid.cpp
index 8e63b58b85..26db03fbab 100644
--- a/src/common/uuid.cpp
+++ b/src/common/uuid.cpp
@@ -1,4 +1,4 @@
-// Copyright 2018 Citra Emulator Project
+// Copyright 2018 yuzu Emulator Project
 // Licensed under GPLv2 or any later version
 // Refer to the license.txt file included.
 
diff --git a/src/common/uuid.h b/src/common/uuid.h
index 4a5e5fa7cc..b8864b34fb 100644
--- a/src/common/uuid.h
+++ b/src/common/uuid.h
@@ -1,9 +1,11 @@
-// Copyright 2018 Citra Emulator Project
+// Copyright 2018 yuzu Emulator Project
 // Licensed under GPLv2 or any later version
 // Refer to the license.txt file included.
 
 #pragma once
 
+#include <string>
+
 #include "common/common_types.h"
 
 namespace Common {
@@ -33,7 +35,7 @@ struct UUID {
     static UUID Generate();
 
     // Set the UUID to {0,0} to be considered an invalid user
-    void Invalidate() {
+    constexpr void Invalidate() {
         uuid = INVALID_UUID;
     }
 
diff --git a/src/core/hle/service/acc/profile_manager.cpp b/src/core/hle/service/acc/profile_manager.cpp
index 767523dbca..49aa5908b4 100644
--- a/src/core/hle/service/acc/profile_manager.cpp
+++ b/src/core/hle/service/acc/profile_manager.cpp
@@ -13,7 +13,7 @@
 
 namespace Service::Account {
 
-using namespace Common;
+using Common::UUID;
 
 struct UserRaw {
     UUID uuid;
@@ -199,7 +199,7 @@ bool ProfileManager::UserExists(UUID uuid) const {
 bool ProfileManager::UserExistsIndex(std::size_t index) const {
     if (index >= MAX_USERS)
         return false;
-    return profiles[index].user_uuid.uuid != INVALID_UUID;
+    return profiles[index].user_uuid.uuid != Common::INVALID_UUID;
 }
 
 /// Opens a specific user
@@ -293,7 +293,7 @@ bool ProfileManager::RemoveUser(UUID uuid) {
 
 bool ProfileManager::SetProfileBase(UUID uuid, const ProfileBase& profile_new) {
     const auto index = GetUserIndex(uuid);
-    if (!index || profile_new.user_uuid == UUID(INVALID_UUID)) {
+    if (!index || profile_new.user_uuid == UUID(Common::INVALID_UUID)) {
         return false;
     }
 
@@ -324,7 +324,7 @@ void ProfileManager::ParseUserSaveFile() {
     }
 
     for (const auto& user : data.users) {
-        if (user.uuid == UUID(INVALID_UUID)) {
+        if (user.uuid == UUID(Common::INVALID_UUID)) {
             continue;
         }
 
diff --git a/src/core/hle/service/mii/mii_manager.cpp b/src/core/hle/service/mii/mii_manager.cpp
index 25dfd8d482..083c62b1e1 100644
--- a/src/core/hle/service/mii/mii_manager.cpp
+++ b/src/core/hle/service/mii/mii_manager.cpp
@@ -12,8 +12,10 @@
 
 namespace Service::Mii {
 
+namespace {
+
 constexpr char MII_SAVE_DATABASE_PATH[] = "/system/save/8000000000000030/MiiDatabase.dat";
-constexpr std::array<char16_t, 11> DEFAULT_MII_NAME = {'y', 'u', 'z', 'u', '\0'};
+constexpr std::array<char16_t, 11> DEFAULT_MII_NAME = {u'y', u'u', u'z', u'u', u'\0'};
 
 // This value was retrieved from HW test
 constexpr MiiStoreData DEFAULT_MII = {
@@ -30,10 +32,10 @@ constexpr MiiStoreData DEFAULT_MII = {
 // Default values taken from multiple real databases
 const MiiDatabase DEFAULT_MII_DATABASE{Common::MakeMagic('N', 'F', 'D', 'B'), {}, {1}, 0, 0};
 
-template <typename T, std::size_t s1, std::size_t s2>
-std::array<T, s2> ResizeArray(const std::array<T, s1>& in) {
-    std::array<T, s2> out{};
-    std::memcpy(out.data(), in.data(), sizeof(T) * std::min(s1, s2));
+template <typename T, std::size_t SourceArraySize, std::size_t DestArraySize>
+std::array<T, DestArraySize> ResizeArray(const std::array<T, SourceArraySize>& in) {
+    std::array<T, DestArraySize> out{};
+    std::memcpy(out.data(), in.data(), sizeof(T) * std::min(SourceArraySize, DestArraySize));
     return out;
 }
 
@@ -163,12 +165,14 @@ MiiStoreData ConvertInfoToStoreData(const MiiInfo& info) {
     return out;
 }
 
+} // namespace
+
 std::u16string MiiInfo::Name() const {
     return Common::UTF16StringFromFixedZeroTerminatedBuffer(name.data(), name.size());
 }
 
 bool operator==(const MiiInfo& lhs, const MiiInfo& rhs) {
-    return std::memcmp(&lhs, &rhs, sizeof(MiiInfo));
+    return std::memcmp(&lhs, &rhs, sizeof(MiiInfo)) == 0;
 }
 
 bool operator!=(const MiiInfo& lhs, const MiiInfo& rhs) {
@@ -188,27 +192,15 @@ MiiInfo MiiManager::CreateRandom(RandomParameters params) {
                 "(STUBBED) called with params={:08X}{:08X}{:08X}, returning default Mii",
                 params.unknown_1, params.unknown_2, params.unknown_3);
 
-    auto new_mii = DEFAULT_MII;
-
-    do {
-        new_mii.uuid = Common::UUID::Generate();
-    } while (IndexOf(new_mii.uuid) == INVALID_INDEX);
-
-    return ConvertStoreDataToInfo(new_mii);
+    return ConvertStoreDataToInfo(CreateMiiWithUniqueUUID());
 }
 
 MiiInfo MiiManager::CreateDefault(u32 index) {
-    auto new_mii = DEFAULT_MII;
+    const auto new_mii = CreateMiiWithUniqueUUID();
 
-    do {
-        new_mii.uuid = Common::UUID::Generate();
-    } while (IndexOf(new_mii.uuid) == INVALID_INDEX);
-
-    ASSERT(index < MAX_MIIS);
-    database.miis[index] = new_mii;
-    std::stable_partition(database.miis.begin(), database.miis.end(),
-                          [](const MiiStoreData& elem) { return elem.uuid; });
+    database.miis.at(index) = new_mii;
 
+    EnsureDatabasePartition();
     return ConvertStoreDataToInfo(new_mii);
 }
 
@@ -253,8 +245,7 @@ bool MiiManager::Remove(Common::UUID uuid) {
         return false;
 
     *iter = MiiStoreData{};
-    std::stable_partition(database.miis.begin(), database.miis.end(),
-                          [](const MiiStoreData& elem) { return elem.uuid; });
+    EnsureDatabasePartition();
     return true;
 }
 
@@ -268,9 +259,9 @@ u32 MiiManager::IndexOf(Common::UUID uuid) const {
     return static_cast<u32>(std::distance(database.miis.begin(), iter));
 }
 
-u32 MiiManager::IndexOf(MiiInfo info) const {
+u32 MiiManager::IndexOf(const MiiInfo& info) const {
     const auto iter =
-        std::find_if(database.miis.begin(), database.miis.end(), [info](const MiiStoreData& elem) {
+        std::find_if(database.miis.begin(), database.miis.end(), [&info](const MiiStoreData& elem) {
             return ConvertStoreDataToInfo(elem) == info;
         });
 
@@ -296,12 +287,11 @@ bool MiiManager::Move(Common::UUID uuid, u32 new_index) {
         database.miis[new_index] = moving;
     }
 
-    std::stable_partition(database.miis.begin(), database.miis.end(),
-                          [](const MiiStoreData& elem) { return elem.uuid; });
+    EnsureDatabasePartition();
     return true;
 }
 
-bool MiiManager::AddOrReplace(MiiStoreData data) {
+bool MiiManager::AddOrReplace(const MiiStoreData& data) {
     const auto index = IndexOf(data.uuid);
 
     if (index == INVALID_INDEX) {
@@ -341,7 +331,11 @@ void MiiManager::WriteToFile() {
     }
 
     save.Resize(sizeof(MiiDatabase));
-    save.WriteBytes(&database, sizeof(MiiDatabase));
+    if (save.WriteBytes(&database, sizeof(MiiDatabase)) != sizeof(MiiDatabase)) {
+        LOG_WARNING(Service_Mii, "Failed to write all data to save file... Data may be malformed "
+                                 "and/or regenerated on next run.");
+        save.Resize(0);
+    }
 }
 
 void MiiManager::ReadFromFile() {
@@ -362,6 +356,20 @@ void MiiManager::ReadFromFile() {
         return;
     }
 
+    EnsureDatabasePartition();
+}
+
+MiiStoreData MiiManager::CreateMiiWithUniqueUUID() const {
+    auto new_mii = DEFAULT_MII;
+
+    do {
+        new_mii.uuid = Common::UUID::Generate();
+    } while (IndexOf(new_mii.uuid) == INVALID_INDEX);
+
+    return new_mii;
+}
+
+void MiiManager::EnsureDatabasePartition() {
     std::stable_partition(database.miis.begin(), database.miis.end(),
                           [](const MiiStoreData& elem) { return elem.uuid; });
 }
diff --git a/src/core/hle/service/mii/mii_manager.h b/src/core/hle/service/mii/mii_manager.h
index 069247cb6d..f7e3d2cf94 100644
--- a/src/core/hle/service/mii/mii_manager.h
+++ b/src/core/hle/service/mii/mii_manager.h
@@ -84,6 +84,8 @@ struct MiiInfo {
     std::u16string Name() const;
 };
 static_assert(sizeof(MiiInfo) == 0x58, "MiiInfo has incorrect size.");
+static_assert(std::has_unique_object_representations_v<MiiInfo>,
+              "All bits of MiiInfo must contribute to its value.");
 
 bool operator==(const MiiInfo& lhs, const MiiInfo& rhs);
 bool operator!=(const MiiInfo& lhs, const MiiInfo& rhs);
@@ -238,15 +240,19 @@ public:
 
     bool Remove(Common::UUID uuid);
     u32 IndexOf(Common::UUID uuid) const;
-    u32 IndexOf(MiiInfo info) const;
+    u32 IndexOf(const MiiInfo& info) const;
 
     bool Move(Common::UUID uuid, u32 new_index);
-    bool AddOrReplace(MiiStoreData data);
+    bool AddOrReplace(const MiiStoreData& data);
 
 private:
     void WriteToFile();
     void ReadFromFile();
 
+    MiiStoreData CreateMiiWithUniqueUUID() const;
+
+    void EnsureDatabasePartition();
+
     MiiDatabase database;
 };