diff --git a/inc/napa/stl/string.h b/inc/napa/stl/string.h
index ae2b98a..130a2d6 100644
--- a/inc/napa/stl/string.h
+++ b/inc/napa/stl/string.h
@@ -12,6 +12,7 @@ namespace napa {
         using BasicString = std::basic_string<CharT, Traits, napa::stl::Allocator<CharT>>;
 
         typedef BasicString<char> String;
+        typedef BasicString<char16_t> U16String;
     }
 }
 
@@ -22,13 +23,25 @@ namespace std {
     template<>
     struct hash<napa::stl::String> : public __hash_base<size_t, napa::stl::String> {
         size_t operator()(const napa::stl::String& s) const noexcept {
-            return std::_Hash_impl::hash(s.data(), s.length());
+            return std::_Hash_impl::hash(s.data(), s.length() * sizeof(char));
         }
     };
 
     template<>
     struct __is_fast_hash<hash<napa::stl::String>> : std::false_type {
     };
+
+    // std::hash specialization for napa::stl::U16String.
+    template<>
+    struct hash<napa::stl::U16String> : public __hash_base<size_t, napa::stl::U16String> {
+        size_t operator()(const napa::stl::U16String& s) const noexcept {
+            return std::_Hash_impl::hash(s.data(), s.length() * sizeof(char16_t));
+        }
+    };
+
+    template<>
+    struct __is_fast_hash<hash<napa::stl::U16String>> : std::false_type {
+    };
 }
 
 #endif
diff --git a/inc/napa/v8-helpers/conversion.h b/inc/napa/v8-helpers/conversion.h
index cbfa7d3..5900de6 100644
--- a/inc/napa/v8-helpers/conversion.h
+++ b/inc/napa/v8-helpers/conversion.h
@@ -22,6 +22,13 @@ namespace v8_helpers {
         return std::string(*utf8Value);
     }
 
+    /// <summary> Convert a v8 value to std::u16string. </summary>
+    template <>
+    inline std::u16string V8ValueTo(const v8::Local<v8::Value>& value) {
+        v8::String::Value utf16Value(value);
+        return std::u16string(reinterpret_cast<const char16_t *>(*utf16Value));
+    }
+
     /// <summary> Convert a v8 value to napa::stl::String. </summary>
     template <>
     inline napa::stl::String V8ValueTo(const v8::Local<v8::Value>& value) {
@@ -29,6 +36,13 @@ namespace v8_helpers {
         return napa::stl::String(*utf8Value);
     }
 
+    /// <summary> Convert a v8 value to napa::stl::U16String. </summary>
+    template <>
+    inline napa::stl::U16String V8ValueTo(const v8::Local<v8::Value>& value) {
+        v8::String::Value utf16Value(value);
+        return napa::stl::U16String(reinterpret_cast<const char16_t *>(*utf16Value));
+    }
+
     /// <summary> Convert a v8 value to a Utf8String. </summary>
     template <>
     inline Utf8String V8ValueTo(const v8::Local<v8::Value>& value) {
diff --git a/inc/napa/v8-helpers/string.h b/inc/napa/v8-helpers/string.h
index d34e3ba..0059d7e 100644
--- a/inc/napa/v8-helpers/string.h
+++ b/inc/napa/v8-helpers/string.h
@@ -20,35 +20,92 @@ namespace v8_helpers {
         return MakeV8String(isolate, str.c_str(), static_cast<int>(str.length()));
     }
 
-    /// <summary> Make a V8 string from std::string. </summary>
+    /// <summary> Make a V8 string from napa::stl::String. </summary>
     inline v8::Local<v8::String> MakeV8String(v8::Isolate *isolate, const napa::stl::String& str) {
         return MakeV8String(isolate, str.c_str(), static_cast<int>(str.length()));
     }
 
+    /// <summary> Make a V8 string by making a copy of const uint16_t*. </summary>
+    inline v8::Local<v8::String> MakeV8String(v8::Isolate *isolate, const uint16_t* str, int length = -1) {
+        return v8::String::NewFromTwoByte(isolate, str, v8::NewStringType::kNormal, length).ToLocalChecked();
+    }
+
+    /// <summary> Make a V8 string by making a copy of const char16_t*. </summary>
+    inline v8::Local<v8::String> MakeV8String(v8::Isolate *isolate, const char16_t* str, int length = -1) {
+        return MakeV8String(isolate, reinterpret_cast<const uint16_t *>(str), length);
+    }
+
+    /// <summary> Make a V8 string from std::u16string. </summary>
+    inline v8::Local<v8::String> MakeV8String(v8::Isolate *isolate, const std::u16string& str) {
+        return MakeV8String(isolate, str.c_str(), static_cast<int>(str.length()));
+    }
+
+    /// <summary> Make a V8 string from napa::stl::U16String. </summary>
+    inline v8::Local<v8::String> MakeV8String(v8::Isolate *isolate, const napa::stl::U16String& str) {
+        return MakeV8String(isolate, str.c_str(), static_cast<int>(str.length()));
+    }
+
+    using ExternalOneByteStringView = v8::ExternalOneByteStringResourceImpl;
+    class ExternalTwoByteStringView : public v8::String::ExternalStringResource {
+    public:
+        ExternalTwoByteStringView() : _data(nullptr), _length(0) {}
+        ExternalTwoByteStringView(const uint16_t* data, size_t length) : _data(data), _length(length) {}
+        const uint16_t* data() const { return _data; }
+        size_t length() const { return _length; }
+
+    private:
+        const uint16_t* _data;
+        size_t _length;
+    };
+
     /// <summary> Make a V8 string from external const char*. </summary>
-    inline v8::Local<v8::String> MakeExternalV8String(v8::Isolate *isolate, const char* data) {
-        // V8 garbage collection frees ExternalOneByteStringResourceImpl.
-        auto externalResource = new v8::ExternalOneByteStringResourceImpl(data, std::strlen(data));
+    /// <remarks> The input data should only contains Latin-1 chars. </remarks>
+    inline v8::Local<v8::String> MakeExternalV8String(v8::Isolate *isolate, const char* data, size_t length) {
+        // V8 garbage collection frees ExternalOneByteStringView.
+        auto externalResource = new ExternalOneByteStringView(data, length);
         return v8::String::NewExternalOneByte(isolate, externalResource).ToLocalChecked();
     }
 
     /// <summary> Make a V8 string from external const char*. </summary>
-    inline v8::Local<v8::String> MakeExternalV8String(v8::Isolate *isolate, const char* data, size_t length) {
-        // V8 garbage collection frees ExternalOneByteStringResourceImpl.
-        auto externalResource = new v8::ExternalOneByteStringResourceImpl(data, length);
-        return v8::String::NewExternalOneByte(isolate, externalResource).ToLocalChecked();
+    /// <remarks> The input data should only contains Latin-1 chars. </remarks>
+    inline v8::Local<v8::String> MakeExternalV8String(v8::Isolate *isolate, const char* data) {
+        return MakeExternalV8String(isolate, data, strlen(data));
     }
 
     /// <summary> Make a V8 string from external std::string. </sumary>
+    /// <remarks> The input data should only contains Latin-1 chars. </remarks>
     inline v8::Local<v8::String> MakeExternalV8String(v8::Isolate *isolate, const std::string& str) {
         return MakeExternalV8String(isolate, str.data(), str.length());
     }
 
-     /// <summary> Make a V8 string from external napa::stl::String. </sumary>
+    /// <summary> Make a V8 string from external napa::stl::String. </sumary>
+    /// <remarks> The input data should only contains Latin-1 chars. </remarks>
     inline v8::Local<v8::String> MakeExternalV8String(v8::Isolate *isolate, const napa::stl::String& str) {
         return MakeExternalV8String(isolate, str.data(), str.length());
     }
 
+    /// <summary> Make a V8 string from external const uint16_t*. </summary>
+    inline v8::Local<v8::String> MakeExternalV8String(v8::Isolate *isolate, const uint16_t* data, size_t length) {
+        // V8 garbage collection frees ExternalTwoByteStringView.
+        auto externalResource = new ExternalTwoByteStringView(data, length);
+        return v8::String::NewExternalTwoByte(isolate, externalResource).ToLocalChecked();
+    }
+
+    /// <summary> Make a V8 string from external const char16_t*. </summary>
+    inline v8::Local<v8::String> MakeExternalV8String(v8::Isolate *isolate, const char16_t* data, size_t length) {
+        return MakeExternalV8String(isolate, reinterpret_cast<const uint16_t *>(data), length);
+    }
+
+    /// <summary> Make a V8 string from external std::u16string. </sumary>
+    inline v8::Local<v8::String> MakeExternalV8String(v8::Isolate *isolate, const std::u16string& str) {
+        return MakeExternalV8String(isolate, str.data(), str.length());
+    }
+
+    /// <summary> Make a V8 string from external napa::stl::U16String. </sumary>
+    inline v8::Local<v8::String> MakeExternalV8String(v8::Isolate *isolate, const napa::stl::U16String& str) {
+        return MakeExternalV8String(isolate, str.data(), str.length());
+    }
+
     /// <summary> Converts a V8 string object to a movable Utf8String which supports an allocator. </summary>
     template <typename Alloc>
     class Utf8StringWithAllocator {
@@ -73,7 +130,7 @@ namespace v8_helpers {
             if (!val->ToString(context).ToLocal(&str)) {
                 return;
             }
-            _length = str->Length();
+            _length = str->Utf8Length();
             _data = _alloc.allocate(_length + 1);
             str->WriteUtf8(_data);
         }
diff --git a/src/module/core-modules/napa/call-context-wrap.cpp b/src/module/core-modules/napa/call-context-wrap.cpp
index 08e6461..4c9155e 100644
--- a/src/module/core-modules/napa/call-context-wrap.cpp
+++ b/src/module/core-modules/napa/call-context-wrap.cpp
@@ -117,7 +117,8 @@ void CallContextWrap::GetArgumentsCallback(v8::Local<v8::String> /*propertyName*
     auto& cppArgs = thisObject->GetRef().GetArguments();
     auto jsArgs = v8::Array::New(isolate, static_cast<int>(cppArgs.size()));
     for (size_t i = 0; i < cppArgs.size(); ++i) {
-        (void)jsArgs->CreateDataProperty(context, static_cast<uint32_t>(i), v8_helpers::MakeExternalV8String(isolate, cppArgs[i]));
+        // TODO: Switch to 2-bytes external string.
+        (void)jsArgs->CreateDataProperty(context, static_cast<uint32_t>(i), v8_helpers::MakeV8String(isolate, cppArgs[i]));
     }
     args.GetReturnValue().Set(jsArgs);
 }
diff --git a/src/module/core-modules/napa/store-wrap.cpp b/src/module/core-modules/napa/store-wrap.cpp
index 9f4f152..923850d 100644
--- a/src/module/core-modules/napa/store-wrap.cpp
+++ b/src/module/core-modules/napa/store-wrap.cpp
@@ -54,7 +54,7 @@ void StoreWrap::SetCallback(const v8::FunctionCallbackInfo<v8::Value>& args) {
     store.Set(
         v8_helpers::V8ValueTo<std::string>(args[0]).c_str(),
         std::make_shared<napa::store::Store::ValueType>(napa::store::Store::ValueType {
-            v8_helpers::V8ValueTo<std::string>(payload.ToLocalChecked()),
+            v8_helpers::V8ValueTo<std::u16string>(payload.ToLocalChecked()),
             std::move(transportContext)
         }));
 }
diff --git a/src/store/store.h b/src/store/store.h
index 6e3e324..c1f8d88 100644
--- a/src/store/store.h
+++ b/src/store/store.h
@@ -20,7 +20,7 @@ namespace store {
         /// Meta-data that is necessary to marshall/unmarshall JS values.
         struct ValueType {
             /// <summary> JSON string from marshalled JS value. </summary>
-            std::string payload;
+            std::u16string payload;
 
             /// <summary> TransportContext that is needed to unmarshall the JS value. </summary>
             napa::transport::TransportContext transportContext;
diff --git a/test/napa-zone/test.ts b/test/napa-zone/test.ts
index 19a1978..e36381e 100644
--- a/test/napa-zone/test.ts
+++ b/test/napa-zone/test.ts
@@ -115,6 +115,21 @@ export function executeWithTransportableReturns(id: string): Promise<any> {
     });
 }
 
+export function executeWithArgsContainingUnicodeString(id: string): Promise<any> {
+    let unicodeStr = "中文 español deutsch English हिन्दी العربية português বাংলা русский 日本語 ਪੰਜਾਬੀ 한국어 தமிழ் עברית";
+    let zone = napa.zone.get(id);
+    return new Promise((resolve, reject) => {
+        zone.execute((str: string) => {
+                var assert = require("assert");
+                let unicodeStr = "中文 español deutsch English हिन्दी العربية português বাংলা русский 日本語 ਪੰਜਾਬੀ 한국어 தமிழ் עברית";
+                assert.equal(str, unicodeStr);
+                return str;
+            }, [unicodeStr])
+            .then ((result: napa.zone.Result) => resolve(result.value))
+            .catch((error: any) => reject(error));
+    });
+}
+
 /// <summary> Memory test helpers. </summary>
 export function crtAllocatorTest(): void {
     let handle = napa.memory.crtAllocator.allocate(10);
diff --git a/test/store-test.ts b/test/store-test.ts
index d170a5c..299e762 100644
--- a/test/store-test.ts
+++ b/test/store-test.ts
@@ -41,8 +41,8 @@ describe('napajs/store', function () {
         assert.equal(store2.id, 'store2');
     });
 
-    it('@napa: store.get', () => {
-        napaZone.execute('./napa-zone/test', "getStoreTest");
+    it('@napa: store.get', async () => {
+        await napaZone.execute('./napa-zone/test', "getStoreTest");
     });
 
     it('simple types: set in node, get in node', () => {
@@ -50,14 +50,14 @@ describe('napajs/store', function () {
         assert.equal(store1.get('a'), 1);
     });
 
-    it('simple types: set in node, get in napa', () => {
+    it('simple types: set in node, get in napa', async () => {
         store1.set('b', 'hi');
-        napaZone.execute('./napa-zone/test', "storeVerifyGet", ['store1', 'b', 'hi']);
+        await napaZone.execute('./napa-zone/test', "storeVerifyGet", ['store1', 'b', 'hi']);
     });
 
-    it('simple types: set in napa, get in napa', () => {
-        napaZone.execute('./napa-zone/test', "storeSet", ['store1', 'c', 1]);
-        napaZone.execute('./napa-zone/test', "storeVerifyGet", ['store1', 'c', 1]);
+    it('simple types: set in napa, get in napa', async () => {
+        await napaZone.execute('./napa-zone/test', "storeSet", ['store1', 'c', 1]);
+        await napaZone.execute('./napa-zone/test', "storeVerifyGet", ['store1', 'c', 1]);
     });
 
     it('simple types: set in napa, get in node', async () => {
@@ -68,20 +68,46 @@ describe('napajs/store', function () {
         });
     });
 
+    let unicodeStr = "中文 español deutsch English हिन्दी العربية português বাংলা русский 日本語 ਪੰਜਾਬੀ 한국어 தமிழ் עברית";
+    let store2 = napa.store.create('store2');
+
+    it('unicode string: set in node, get in node', () => {
+        store2.set('a', unicodeStr);
+        assert.equal(store2.get('a'), unicodeStr);
+    });
+
+    it('unicode string: set in node, get in napa', async () => {
+        store2.set('b', unicodeStr);
+        await napaZone.execute('./napa-zone/test', "storeVerifyGet", ['store2', 'b', unicodeStr]);
+    });
+
+    it('unicode string: set in napa, get in napa', async () => {
+        await napaZone.execute('./napa-zone/test', "storeSet", ['store2', 'c', unicodeStr]);
+        await napaZone.execute('./napa-zone/test', "storeVerifyGet", ['store2', 'c', unicodeStr]);
+    });
+
+    it('unicode string: set in napa, get in node', async () => {
+        await napaZone.execute('./napa-zone/test', "storeSet", ['store2', 'd', { a: 1, b: unicodeStr}]);
+        assert.deepEqual(store2.get('d'), {
+            a: 1,
+            b: unicodeStr
+        });
+    });
+
     it('transportable types: set in node, get in node', () => {
         store1.set('a', napa.memory.crtAllocator);
         assert.deepEqual(store1.get('a'), napa.memory.crtAllocator);
     });
 
-    it('transportable types: set in node, get in napa', () => {
+    it('transportable types: set in node, get in napa', async () => {
         store1.set('b', napa.memory.defaultAllocator);
-        napaZone.execute('./napa-zone/test', "storeVerifyGet", ['store1', 'b', napa.memory.defaultAllocator]);
+        await napaZone.execute('./napa-zone/test', "storeVerifyGet", ['store1', 'b', napa.memory.defaultAllocator]);
     });
 
     it('transportable types: set in napa, get in napa', async () => {
         // We have to compare handle in this case, since napa.memory.defaultAllocator retrieved from napa zone will have 2+ refCount.
         await napaZone.execute('./napa-zone/test', "storeSet", ['store1', 'e', napa.memory.defaultAllocator]);
-        napaZone.execute('./napa-zone/test', "storeGetCompareHandle", ['store1', 'e', napa.memory.defaultAllocator.handle]);
+        await napaZone.execute('./napa-zone/test', "storeGetCompareHandle", ['store1', 'e', napa.memory.defaultAllocator.handle]);
     });
 
     it('transportable types: set in napa, get in node', async () => {
@@ -95,14 +121,14 @@ describe('napajs/store', function () {
         assert.equal(store1.get('g').toString(), (() => { return 0; }).toString());
     });
 
-    it('function type: set in node, get in napa', () => {
+    it('function type: set in node, get in napa', async () => {
         store1.set('h', () => { return 0; });
-        napaZone.execute('./napa-zone/test', "storeVerifyGet", ['store1', 'h', () => { return 0; }]);
+        await napaZone.execute('./napa-zone/test', "storeVerifyGet", ['store1', 'h', () => { return 0; }]);
     });
 
     it('function type: set in napa, get in napa', async () => {
         await napaZone.execute('./napa-zone/test', "storeSet", ['store1', 'i', () => { return 0; }]);
-        napaZone.execute('./napa-zone/test', "storeVerifyGet", ['store1', 'i', () => { return 0; }]);
+        await napaZone.execute('./napa-zone/test', "storeVerifyGet", ['store1', 'i', () => { return 0; }]);
     });
 
     it('function type: set in napa, get in node', async () => {
@@ -118,15 +144,15 @@ describe('napajs/store', function () {
         store1.delete('not-exist');
     });
 
-    it('delete in node, check in napa', () => {
+    it('delete in node, check in napa', async () => {
         assert(store1.has('b'));
         store1.delete('b');
-        napaZone.execute('./napa-zone/test', "storeVerifyNotExist", ['store1', 'b']);
+        await napaZone.execute('./napa-zone/test', "storeVerifyNotExist", ['store1', 'b']);
     });
 
     it('delete in napa, check in napa', async () => {
         await napaZone.execute('./napa-zone/test', "storeDelete", ['store1', 'c']);
-        napaZone.execute('./napa-zone/test', "storeVerifyNotExist", ['store1', 'c']);
+        await napaZone.execute('./napa-zone/test', "storeVerifyNotExist", ['store1', 'c']);
     })
 
     it('delete in napa, check in node', async () => {
diff --git a/test/transport-test.ts b/test/transport-test.ts
index 7d3276c..13b9451 100644
--- a/test/transport-test.ts
+++ b/test/transport-test.ts
@@ -60,7 +60,7 @@ describe('napajs/transport', () => {
         });
 
         it('@node: addon transportable', () => {
-           t.addonTransportTest();
+            t.addonTransportTest();
         });
 
         it('@napa: addon transportable', () => {
@@ -68,7 +68,7 @@ describe('napajs/transport', () => {
         });
 
         it('@node: function transportable', () => {
-           t.functionTransportTest();
+            t.functionTransportTest();
         });
 
         it('@napa: function transportable', () => {
diff --git a/test/zone-test.ts b/test/zone-test.ts
index 3e3b82f..c143e6f 100644
--- a/test/zone-test.ts
+++ b/test/zone-test.ts
@@ -508,6 +508,44 @@ describe('napajs/zone', function () {
                 });
         });
 
+        let unicodeStr = "中文 español deutsch English हिन्दी العربية português বাংলা русский 日本語 ਪੰਜਾਬੀ 한국어 தமிழ் עברית"; // len = 92
+
+        it('@node: -> node zone with args containing unicode string', () => {
+            return napa.zone.current.execute((str: string) => {
+                var assert = require("assert");
+                let unicodeStr = "中文 español deutsch English हिन्दी العربية português বাংলা русский 日本語 ਪੰਜਾਬੀ 한국어 தமிழ் עברית";
+                assert.equal(str, unicodeStr);
+                return str;
+            }, [unicodeStr]).then((result: napa.zone.Result) => {
+                assert.equal(result.value, unicodeStr);
+            });
+        });
+
+        it('@node: -> napa zone with args containing unicode string', () => {
+            return napaZone1.execute((str: string) => {
+                var assert = require("assert");
+                let unicodeStr = "中文 español deutsch English हिन्दी العربية português বাংলা русский 日本語 ਪੰਜਾਬੀ 한국어 தமிழ் עברית";
+                assert.equal(str, unicodeStr);
+                return unicodeStr;
+            }, [unicodeStr]).then((result: napa.zone.Result) => {
+                assert.equal(result.value, unicodeStr);
+            });
+        });
+
+        it('@napa: -> napa zone with args containing unicode string', () => {
+            return napaZone1.execute('./napa-zone/test', "executeWithArgsContainingUnicodeString", ['napa-zone2'])
+                .then((result: napa.zone.Result) => {
+                    assert.equal(result.value, unicodeStr);
+                });
+        });
+
+        it('@napa: -> node zone with args containing unicode string', () => {
+            return napaZone1.execute('./napa-zone/test', "executeWithArgsContainingUnicodeString", ['node'])
+                .then((result: napa.zone.Result) => {
+                    assert.equal(result.value, unicodeStr);
+                });
+        });
+
         it.skip('@node: -> napa zone with timeout and succeed', () => {
             return napaZone1.execute('./napa-zone/test', 'waitMS', [1], {timeout: 100});
         });