diff --git a/src/android/android.gyp b/src/android/android.gyp
index 8280b45..fc4c08b 100644
--- a/src/android/android.gyp
+++ b/src/android/android.gyp
@@ -225,28 +225,20 @@
     {
       'target_name': 'assets_mozc_dataset',
       'type': 'none',
-      'conditions': [
-        ['use_separate_dataset==1',
-          {
-            'actions': [
-              {
-                'action_name': 'assets_copy_dataset',
-                'inputs': [
-                    '<(mozc_dataset)',
-                ],
-                'outputs': [
-                  '<(sdk_asset_dir)/mozc.imy',
-                ],
-                'action': [
-                  # Note that multiple output files cannot be handled
-                  # by copy_file script.
-                  '<@(copy_file)', '<@(_inputs)', '<@(_outputs)',
-                ],
-              },
-            ],
-          },
-        ],
-      ],
+      'actions': [{
+        'action_name': 'assets_copy_dataset',
+        'inputs': [
+          '<(mozc_dataset)',
+        ],
+        'outputs': [
+          '<(sdk_asset_dir)/mozc.imy',
+        ],
+        'action': [
+          # Note that multiple output files cannot be handled
+          # by copy_file script.
+          '<@(copy_file)', '<@(_inputs)', '<@(_outputs)',
+        ],
+      }],
     },
     {
       # CAVEAT:
diff --git a/src/build_mozc.py b/src/build_mozc.py
index 7a68453..809aa35 100644
--- a/src/build_mozc.py
+++ b/src/build_mozc.py
@@ -731,15 +731,12 @@
   # Dictionary configuration
   if target_platform == 'Android':
     gyp_options.extend(['-D', 'dictionary=small'])
-    gyp_options.extend(['-D', 'use_separate_dataset=1'])
     gyp_options.extend(['-D', 'use_1byte_cost_for_connection_data=1'])
   elif target_platform == 'NaCl':
     gyp_options.extend(['-D', 'dictionary=desktop'])
-    gyp_options.extend(['-D', 'use_separate_dataset=0'])
     gyp_options.extend(['-D', 'use_1byte_cost_for_connection_data=0'])
   else:
     gyp_options.extend(['-D', 'dictionary=desktop'])
-    gyp_options.extend(['-D', 'use_separate_dataset=0'])
     gyp_options.extend(['-D', 'use_1byte_cost_for_connection_data=0'])
 
   if target_platform == 'NaCl':
diff --git a/src/converter/converter_test.gyp b/src/converter/converter_test.gyp
index 7909061..a5be6fb 100644
--- a/src/converter/converter_test.gyp
+++ b/src/converter/converter_test.gyp
@@ -49,7 +49,6 @@
       'dependencies': [
         '../composer/composer.gyp:composer',
         '../config/config.gyp:config_handler',
-        '../data_manager/data_manager_test.gyp:scoped_data_manager_initializer_for_testing',
         '../data_manager/testing/mock_data_manager.gyp:mock_data_manager',
         '../dictionary/dictionary.gyp:dictionary_mock',
         '../dictionary/dictionary.gyp:suffix_dictionary',
diff --git a/src/data/version/mozc_version_template.txt b/src/data/version/mozc_version_template.txt
index 34333b8..9627dc9 100644
--- a/src/data/version/mozc_version_template.txt
+++ b/src/data/version/mozc_version_template.txt
@@ -1,6 +1,6 @@
 MAJOR=2
 MINOR=18
-BUILD=2552
+BUILD=2553
 REVISION=102
 # CAUTION: NACL_DICTIONARY_VERSION is going to be migrated to ENGINE_VERSION.
 # NACL_DICTIONARY_VERSION is the target version of the system dictionary to be
diff --git a/src/data_manager/data_manager_test.gyp b/src/data_manager/data_manager_test.gyp
index 37122bf..8616f78 100644
--- a/src/data_manager/data_manager_test.gyp
+++ b/src/data_manager/data_manager_test.gyp
@@ -50,21 +50,6 @@
       ],
     },
     {
-      'target_name': 'scoped_data_manager_initializer_for_testing',
-      'type': 'static_library',
-      'toolsets': [ 'target' ],
-      'sources': [
-        'scoped_data_manager_initializer_for_testing.cc',
-      ],
-      'conditions': [
-        ['target_platform=="Android"', {
-          'dependencies': [
-            ':scoped_android_data_manager_initializer_for_testing'
-          ],
-        }],
-      ],
-    },
-    {
       'target_name': 'dataset_writer_test',
       'type': 'executable',
       'toolsets': [ 'target' ],
@@ -107,18 +92,4 @@
       ],
     },
   ],
-  'conditions': [
-    ['target_platform=="Android"', {
-      'targets': [
-        {
-          'target_name': 'scoped_android_data_manager_initializer_for_testing',
-          'type': 'static_library',
-          'toolsets': [ 'target' ],
-          'sources': [
-            'android/scoped_android_data_manager_initializer_for_testing.cc',
-          ],
-        },
-      ],
-    }],
-  ],
 }
diff --git a/src/data_manager/oss/oss_data_manager.cc b/src/data_manager/oss/oss_data_manager.cc
index a465d98..a19ae5f 100644
--- a/src/data_manager/oss/oss_data_manager.cc
+++ b/src/data_manager/oss/oss_data_manager.cc
@@ -36,15 +36,8 @@
 namespace oss {
 namespace {
 
-const char *g_mozc_data_address = nullptr;
-size_t g_mozc_data_size = 0;
-
-#ifdef MOZC_USE_SEPARATE_DATASET
-const EmbeddedFile kOssMozcDataSet = {nullptr, 0};
-#else
 // kOssMozcDataSet is embedded.
 #include "data_manager/oss/mozc_imy.h"
-#endif  // MOZC_USE_SEPARATE_DATASET
 
 #ifndef MOZC_DATASET_MAGIC_NUMBER
 #error "MOZC_DATASET_MAGIC_NUMBER is not defined by build system"
@@ -56,29 +49,11 @@
 
 OssDataManager::OssDataManager() {
   const StringPiece magic(kMagicNumber, arraysize(kMagicNumber) - 1);
-  if (g_mozc_data_address != nullptr) {
-    const StringPiece data(g_mozc_data_address, g_mozc_data_size);
-    CHECK_EQ(Status::OK, InitFromArray(data, magic))
-        << "Image set by SetMozcDataSet() is broken";
-    return;
-  }
-#ifdef MOZC_USE_SEPARATE_DATASET
-  LOG(FATAL)
-      << "When MOZC_USE_SEPARATE_DATASET build flag is defined, "
-      << "OssDataManager::SetMozcDataSet() must be called before "
-      << "instantiation of OssDataManager instances.";
-#endif  // MOZC_USE_SEPARATE_DATASET
   CHECK_EQ(Status::OK, InitFromArray(LoadEmbeddedFile(kOssMozcDataSet), magic))
       << "Embedded mozc_imy.h for OSS is broken";
 }
 
 OssDataManager::~OssDataManager() = default;
 
-// Both pointers can be nullptr when the DataManager is reset on testing.
-void OssDataManager::SetMozcDataSet(void *address, size_t size) {
-  g_mozc_data_address = reinterpret_cast<char *>(address);
-  g_mozc_data_size = size;
-}
-
 }  // namespace oss
 }  // namespace mozc
diff --git a/src/data_manager/oss/oss_data_manager.h b/src/data_manager/oss/oss_data_manager.h
index 3e9aca0..e2e5826 100644
--- a/src/data_manager/oss/oss_data_manager.h
+++ b/src/data_manager/oss/oss_data_manager.h
@@ -36,12 +36,12 @@
 namespace mozc {
 namespace oss {
 
+// This is a simple wrapper of DataManager that uses the embedded OSS data set.
+// Note that linking against this module embeds OSS data set into executable.
 class OssDataManager : public DataManager {
  public:
   OssDataManager();
   ~OssDataManager() override;
-
-  static void SetMozcDataSet(void *address, size_t size);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(OssDataManager);
diff --git a/src/data_manager/scoped_data_manager_initializer_for_testing.cc b/src/data_manager/scoped_data_manager_initializer_for_testing.cc
deleted file mode 100644
index 367117e..0000000
--- a/src/data_manager/scoped_data_manager_initializer_for_testing.cc
+++ /dev/null
@@ -1,40 +0,0 @@
-// Copyright 2010-2016, Google Inc.
-// All rights reserved.
-//
-// Redistribution and use in source and binary forms, with or without
-// modification, are permitted provided that the following conditions are
-// met:
-//
-//     * Redistributions of source code must retain the above copyright
-// notice, this list of conditions and the following disclaimer.
-//     * Redistributions in binary form must reproduce the above
-// copyright notice, this list of conditions and the following disclaimer
-// in the documentation and/or other materials provided with the
-// distribution.
-//     * Neither the name of Google Inc. nor the names of its
-// contributors may be used to endorse or promote products derived from
-// this software without specific prior written permission.
-//
-// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
-#include "data_manager/scoped_data_manager_initializer_for_testing.h"
-
-namespace mozc {
-
-scoped_data_manager_initializer_for_testing::
-    scoped_data_manager_initializer_for_testing() {}
-
-scoped_data_manager_initializer_for_testing::
-    ~scoped_data_manager_initializer_for_testing() {}
-
-}  // namespace mozc
diff --git a/src/data_manager/scoped_data_manager_initializer_for_testing.h b/src/data_manager/scoped_data_manager_initializer_for_testing.h
deleted file mode 100644
index c5c318d..0000000
--- a/src/data_manager/scoped_data_manager_initializer_for_testing.h
+++ /dev/null
@@ -1,57 +0,0 @@
-// Copyright 2010-2016, Google Inc.
-// All rights reserved.
-//
-// Redistribution and use in source and binary forms, with or without
-// modification, are permitted provided that the following conditions are
-// met:
-//
-//     * Redistributions of source code must retain the above copyright
-// notice, this list of conditions and the following disclaimer.
-//     * Redistributions in binary form must reproduce the above
-// copyright notice, this list of conditions and the following disclaimer
-// in the documentation and/or other materials provided with the
-// distribution.
-//     * Neither the name of Google Inc. nor the names of its
-// contributors may be used to endorse or promote products derived from
-// this software without specific prior written permission.
-//
-// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
-#ifndef MOZC_DATA_MANAGER_SCOPED_DATA_MANAGER_INITIALIZER_FOR_TESTING_H_
-#define MOZC_DATA_MANAGER_SCOPED_DATA_MANAGER_INITIALIZER_FOR_TESTING_H_
-
-#include "base/port.h"
-
-#ifdef OS_ANDROID
-#include "data_manager/android/scoped_android_data_manager_initializer_for_testing.h"
-#endif  // OS_ANDROID
-
-namespace mozc {
-
-class scoped_data_manager_initializer_for_testing {
- public:
-  scoped_data_manager_initializer_for_testing();
-  ~scoped_data_manager_initializer_for_testing();
-
- private:
-#ifdef OS_ANDROID
-  mozc::android::scoped_android_data_manager_initializer_for_testing
-      scoped_android_data_manager_initializer_for_testing_;
-#endif  // OS_ANDROID
-
-  DISALLOW_COPY_AND_ASSIGN(scoped_data_manager_initializer_for_testing);
-};
-
-}  // namespace mozc
-
-#endif  // MOZC_DATA_MANAGER_SCOPED_DATA_MANAGER_INITIALIZER_FOR_TESTING_H_
diff --git a/src/gyp/defines.gypi b/src/gyp/defines.gypi
index 2cb8be1..8124434 100644
--- a/src/gyp/defines.gypi
+++ b/src/gyp/defines.gypi
@@ -38,9 +38,6 @@
 
     # a flag whether the current build is dev-channel or not.
     'channel_dev%': '0',
-
-    # a flag whether the dataset is embedded or separated (for Android).
-    'use_separate_dataset%': '0',
 
     # enable_cloud_handwriting represents if cloud handwriting feature is
     # enabled or not.
@@ -90,9 +87,6 @@
       ['channel_dev==1', {
         'defines': ['CHANNEL_DEV'],
       }],
-      ['use_separate_dataset==1', {
-        'defines': ['MOZC_USE_SEPARATE_DATASET'],
-      }],
       ['enable_cloud_handwriting==1', {
         'defines': ['ENABLE_CLOUD_HANDWRITING'],
       }],
diff --git a/src/prediction/prediction_test.gyp b/src/prediction/prediction_test.gyp
index 88d1f7f..e69e71e 100644
--- a/src/prediction/prediction_test.gyp
+++ b/src/prediction/prediction_test.gyp
@@ -49,7 +49,6 @@
         '../converter/converter_base.gyp:immutable_converter',
         '../converter/converter_base.gyp:segmenter',
         '../converter/converter_base.gyp:segments',
-        '../data_manager/data_manager_test.gyp:scoped_data_manager_initializer_for_testing',
         '../data_manager/testing/mock_data_manager.gyp:mock_data_manager',
         '../dictionary/dictionary.gyp:dictionary',
         '../dictionary/dictionary.gyp:dictionary_mock',
diff --git a/src/prediction/predictor_test.cc b/src/prediction/predictor_test.cc
index 494286c..64e1aa5 100644
--- a/src/prediction/predictor_test.cc
+++ b/src/prediction/predictor_test.cc
@@ -39,7 +39,6 @@
 #include "composer/composer.h"
 #include "config/config_handler.h"
 #include "converter/segments.h"
-#include "data_manager/scoped_data_manager_initializer_for_testing.h"
 #include "data_manager/testing/mock_data_manager.h"
 #include "dictionary/dictionary_mock.h"
 #include "dictionary/pos_matcher.h"
@@ -67,24 +66,23 @@
 
 class CheckCandSizePredictor : public PredictorInterface {
  public:
-  explicit CheckCandSizePredictor(int expected_cand_size) :
-      expected_cand_size_(expected_cand_size),
-      predictor_name_("CheckCandSizePredictor") {
-  }
-  virtual bool PredictForRequest(const ConversionRequest &request,
-                                 Segments *segments) const {
+  explicit CheckCandSizePredictor(int expected_cand_size)
+      : expected_cand_size_(expected_cand_size),
+        predictor_name_("CheckCandSizePredictor") {}
+
+  bool PredictForRequest(const ConversionRequest &request,
+                         Segments *segments) const override {
     EXPECT_EQ(expected_cand_size_, segments->max_prediction_candidates_size());
     return true;
   }
-  virtual const string &GetPredictorName() const {
+
+  const string &GetPredictorName() const override {
     return predictor_name_;
   }
 
  private:
-  int expected_cand_size_;
+  const int expected_cand_size_;
   const string predictor_name_;
-  scoped_data_manager_initializer_for_testing
-      scoped_data_manager_initializer_for_testing_;
 };
 
 class NullPredictor : public PredictorInterface {
@@ -92,8 +90,9 @@
   explicit NullPredictor(bool ret)
       : return_value_(ret), predict_called_(false),
         predictor_name_("NullPredictor") {}
-  virtual bool PredictForRequest(const ConversionRequest &request,
-                                 Segments *segments) const {
+
+  bool PredictForRequest(const ConversionRequest &request,
+                         Segments *segments) const override {
     predict_called_ = true;
     return return_value_;
   }
@@ -102,11 +101,11 @@
     return predict_called_;
   }
 
-  virtual void Clear() {
+  void Clear() {
     predict_called_ = false;
   }
 
-  virtual const string &GetPredictorName() const {
+  const string &GetPredictorName() const override {
     return predictor_name_;
   }
 
@@ -118,8 +117,8 @@
 
 class MockPredictor : public PredictorInterface {
  public:
-  MockPredictor() {}
-  virtual ~MockPredictor() {}
+  MockPredictor() = default;
+  ~MockPredictor() override = default;
   MOCK_CONST_METHOD2(
       PredictForRequest,
       bool(const ConversionRequest &request, Segments *segments));
@@ -130,7 +129,7 @@
 
 class MobilePredictorTest : public ::testing::Test {
  protected:
-  virtual void SetUp() {
+  void SetUp() override {
     config_.reset(new config::Config);
     config::ConfigHandler::GetDefaultConfig(config_.get());
 
diff --git a/src/session/session_handler_stress_test.cc b/src/session/session_handler_stress_test.cc
index 2465e67..5367014 100644
--- a/src/session/session_handler_stress_test.cc
+++ b/src/session/session_handler_stress_test.cc
@@ -36,7 +36,6 @@
 
 #include "base/file_util.h"
 #include "base/port.h"
-#include "data_manager/scoped_data_manager_initializer_for_testing.h"
 #include "engine/engine_factory.h"
 #include "protocol/commands.pb.h"
 #include "session/random_keyevents_generator.h"
@@ -64,18 +63,7 @@
 using session::testing::SessionHandlerTestBase;
 using session::testing::TestSessionClient;
 
-class SessionHandlerStressTest : public SessionHandlerTestBase {
- protected:
-  virtual EngineInterface *CreateEngine() {
-    return EngineFactory::Create();
-  }
-
- private:
-  scoped_data_manager_initializer_for_testing
-      scoped_data_manager_initializer_for_testing_;
-};
-
-TEST_F(SessionHandlerStressTest, BasicStressTest) {
+TEST(SessionHandlerStressTest, BasicStressTest) {
   vector<commands::KeyEvent> keys;
   commands::Output output;
   std::unique_ptr<EngineInterface> engine(EngineFactory::Create());
diff --git a/src/session/session_handler_test_util.h b/src/session/session_handler_test_util.h
index 4267b71..bfbcc12 100644
--- a/src/session/session_handler_test_util.h
+++ b/src/session/session_handler_test_util.h
@@ -36,7 +36,6 @@
 #include <string>
 
 #include "base/port.h"
-#include "data_manager/scoped_data_manager_initializer_for_testing.h"
 #include "protocol/commands.pb.h"
 #include "protocol/config.pb.h"
 #include "testing/base/public/gunit.h"
@@ -94,9 +93,6 @@
   int32 flags_last_command_timeout_backup_;
   int32 flags_last_create_session_timeout_backup_;
   bool flags_restricted_backup_;
-
-  scoped_data_manager_initializer_for_testing
-      scoped_data_manager_initializer_for_testing_;
   usage_stats::scoped_usage_stats_enabler usage_stats_enabler_;
 
   DISALLOW_COPY_AND_ASSIGN(SessionHandlerTestBase);
diff --git a/src/session/session_regression_test.cc b/src/session/session_regression_test.cc
index ad5ce58..d8494e8 100644
--- a/src/session/session_regression_test.cc
+++ b/src/session/session_regression_test.cc
@@ -41,7 +41,6 @@
 #include "composer/table.h"
 #include "config/config_handler.h"
 #include "converter/segments.h"
-#include "data_manager/scoped_data_manager_initializer_for_testing.h"
 #include "engine/engine_factory.h"
 #include "protocol/candidates.pb.h"
 #include "protocol/commands.pb.h"
@@ -56,8 +55,6 @@
 #include "testing/base/public/googletest.h"
 #include "testing/base/public/gunit.h"
 
-DECLARE_string(test_srcdir);
-DECLARE_string(test_tmpdir);
 DECLARE_bool(use_history_rewriter);
 
 namespace mozc {
@@ -86,9 +83,9 @@
 
 }  // namespace
 
-class SessionRegressionTest : public testing::Test {
+class SessionRegressionTest : public ::testing::Test {
  protected:
-  virtual void SetUp() {
+  void SetUp() override {
     SystemUtil::SetUserProfileDirectory(FLAGS_test_tmpdir);
 
     orig_use_history_rewriter_ = FLAGS_use_history_rewriter;
@@ -103,7 +100,7 @@
     CHECK(session_.get());
   }
 
-  virtual void TearDown() {
+  void TearDown() override {
     // just in case, reset the config in test_tmpdir
     config::Config config;
     config::ConfigHandler::GetDefaultConfig(&config);
@@ -160,8 +157,6 @@
   std::unique_ptr<session::Session> session_;
   std::unique_ptr<composer::Table> table_;
   config::Config config_;
-  scoped_data_manager_initializer_for_testing
-      scoped_data_manager_initializer_for_testing_;
 };
 
 
diff --git a/src/session/session_test.gyp b/src/session/session_test.gyp
index d2d98f9..c7c59d2 100644
--- a/src/session/session_test.gyp
+++ b/src/session/session_test.gyp
@@ -42,7 +42,6 @@
       'dependencies': [
         '../base/base.gyp:base',
         '../config/config.gyp:config_handler',
-        '../data_manager/data_manager_test.gyp:scoped_data_manager_initializer_for_testing',
         '../engine/engine.gyp:engine_factory',
         '../engine/engine.gyp:mock_data_engine_factory',
         '../protocol/protocol.gyp:commands_proto',
@@ -98,7 +97,6 @@
         'session_regression_test.cc',
       ],
       'dependencies': [
-        '../data_manager/data_manager_test.gyp:scoped_data_manager_initializer_for_testing',
         '../engine/engine.gyp:engine_factory',
         '../testing/testing.gyp:gtest_main',
         'session.gyp:session',
@@ -248,7 +246,6 @@
         'session_handler_stress_test.cc'
       ],
       'dependencies': [
-        '../data_manager/data_manager_test.gyp:scoped_data_manager_initializer_for_testing',
         '../engine/engine.gyp:engine_factory',
         '../testing/testing.gyp:gtest_main',
         'session.gyp:random_keyevents_generator',