diff --git a/Unvirt/CmdHelper.cpp b/Unvirt/CmdHelper.cpp
index dfb03f0..36cb47b 100644
--- a/Unvirt/CmdHelper.cpp
+++ b/Unvirt/CmdHelper.cpp
@@ -211,20 +211,27 @@ namespace Unvirt::CmdHelper {
 	void HelpDocument::Print() {
 		for (auto& cmd : m_Results) {
 			// syntax
-			YYCC::ConsoleHelper::WriteLine(u8"Syntax: ");
+			// check whether all description of argument are emtpty.
+			bool empty_arg_desc = true;
+			YYCC::ConsoleHelper::Write(YYCC_COLOR_LIGHT_YELLOW(u8"Syntax: "));
 			for (const auto& arg : cmd.m_ArgDesc) {
+				if (!arg.m_Desc.empty()) empty_arg_desc = false;
 				YYCC::ConsoleHelper::Format(u8"%s ", arg.m_Name.c_str());
 			}
 			YYCC::ConsoleHelper::WriteLine(u8"");
 			// command description
 			if (!cmd.m_CmdDesc.empty()) {
-				YYCC::ConsoleHelper::FormatLine(u8"Description: %s", cmd.m_CmdDesc.c_str());
+				YYCC::ConsoleHelper::FormatLine(YYCC_COLOR_LIGHT_YELLOW(u8"Description: ") "%s", cmd.m_CmdDesc.c_str());
 			}
 			// argument description
-			YYCC::ConsoleHelper::WriteLine(u8"Arguments:");
-			for (auto& arg : cmd.m_ArgDesc) {
-				if (!arg.m_Desc.empty()) {
-					YYCC::ConsoleHelper::FormatLine(u8"\t%s: %s", arg.m_Name.c_str(), arg.m_Desc.c_str());
+			if (!empty_arg_desc) {
+				YYCC::ConsoleHelper::WriteLine(YYCC_COLOR_LIGHT_YELLOW(u8"Arguments:"));
+				for (auto& arg : cmd.m_ArgDesc) {
+					if (!arg.m_Desc.empty()) {
+						YYCC::ConsoleHelper::FormatLine(u8"\t" YYCC_COLOR_LIGHT_GREEN("%s") ": % s",
+							arg.m_Name.c_str(), arg.m_Desc.c_str()
+						);
+					}
 				}
 			}
 			// space between each commands
@@ -465,7 +472,7 @@ if (!this->IsRootNode()) { \
 		const ConflictSet& Choice::GetConflictSet() { return m_ConflictSet; }
 		std::u8string Choice::GetHelpSymbol() {
 			return YYCC::StringHelper::Printf(u8"[%s]",
-				YYCC::StringHelper::Join(m_Vocabulary, u8" | ").c_str()
+				YYCC::StringHelper::Join(m_Vocabulary.begin(), m_Vocabulary.end(), u8" | ").c_str()
 			);
 		}
 		bool Choice::BeginConsume(const std::u8string& cur_cmd, ArgumentsMap& am) {
diff --git a/Unvirt/CmdHelper.hpp b/Unvirt/CmdHelper.hpp
index 0da8d01..1bd6fe0 100644
--- a/Unvirt/CmdHelper.hpp
+++ b/Unvirt/CmdHelper.hpp
@@ -137,8 +137,8 @@ namespace Unvirt::CmdHelper {
 			if (finder == m_Data.end())
 				throw std::runtime_error("try to get a non-existent key.");
 			// get stored value data
-			const AMItems::AbstractItem& value = *finder->second.get();
-			return static_cast<const _Ty&>(value);
+			const _Ty* value = static_cast<const _Ty*>(finder->second.get());
+			return *value;
 		}
 		void Remove(const std::u8string_view& key) {
 			// check argument
@@ -150,17 +150,24 @@ namespace Unvirt::CmdHelper {
 		}
 	};
 
+	// Forward declaration for Nodes::AbstractNode
+	namespace Nodes { class AbstractNode; }
+
 	class HelpDocument {
+		friend class Nodes::AbstractNode;
 	public:
 		HelpDocument();
 		~HelpDocument();
 		YYCC_DEF_CLS_COPY_MOVE(HelpDocument);
 
 	public:
+		void Print();
+
+		// AbstractNode used
+	protected:
 		void Push(const std::u8string& arg_name, const std::u8string& arg_desc);
 		void Pop();
 		void Terminate(std::u8string& command_desc);
-		void Print();
 
 	protected:
 		struct StackItem {
@@ -345,14 +352,16 @@ namespace Unvirt::CmdHelper {
 			 * @return Return self for chain calling.
 			*/
 			template<class _Ty, std::enable_if_t<std::is_base_of_v<AbstractNode, _Ty> && !std::is_same_v<AbstractNode, _Ty>, int> = 0>
-			AbstractNode& Then(_Ty&& node) {
+			AbstractNode& Then(AbstractNode& node) {
 				// create node first
-				auto new_node = std::make_shared<_Ty>(std::forward<_Ty>(node));
+				auto new_node = std::make_shared<_Ty>(static_cast<_Ty&>(node));
+				// get its abstract pointer for checking
+				AbstractNode* new_node_ptr = new_node.get();
 				// check root node.
-				if (new_node->IsRootNode())
+				if (new_node_ptr->IsRootNode())
 					throw std::invalid_argument("root node should not be inserted as child node.");
 				// check conflict
-				const auto& new_node_set = new_node->GetConflictSet();
+				const auto& new_node_set = new_node_ptr->GetConflictSet();
 				for (auto& node : m_Nodes) {
 					const auto& node_set = node->GetConflictSet();
 					if (new_node_set.IsConflictWith(node_set))
@@ -528,23 +537,4 @@ namespace Unvirt::CmdHelper {
 		Nodes::RootNode m_RootNode;
 	};
 
-	//class CommandRoot : public AbstractNode {
-	//public:
-	//	CommandRoot();
-	//	virtual ~CommandRoot();
-	//	YYCC_DEL_CLS_COPY_MOVE(CommandRoot);
-
-	//	// Root use special consume and help functions.
-	//	bool RootConsume(std::deque<std::string>&);
-	//	HelpDocument* RootHelp();
-
-	//public:
-	//protected:
-	//	virtual NodeType GetNodeType() override { throw std::logic_error("Root can not be called."); }
-	//	virtual bool IsConflictWith(AbstractNode*) override { throw std::logic_error("Root can not be called."); }
-	//	virtual std::string GetHelpSymbol()  override { throw std::logic_error("Root can not be called."); }
-	//	virtual bool BeginAccept(const std::string&, ArgumentsMap*) override { throw std::logic_error("Root can not be called."); }
-	//	virtual void EndAccept(ArgumentsMap*) override { throw std::logic_error("Root can not be called."); }
-	//};
-
 }