diff --git a/src/sammo/DummySession.php b/src/sammo/DummySession.php
index 13d8cf9c..a8265e55 100644
--- a/src/sammo/DummySession.php
+++ b/src/sammo/DummySession.php
@@ -17,19 +17,9 @@ namespace sammo;
  */
 class DummySession extends Session
 {
-    private $writeClosed = false;
-    private $sessionInfo = [];
+    protected $sessionInfo = [];
 
-    public static function getInstance(): Session
-    {
-        static $inst = null;
-        if ($inst === null) {
-            $inst = new DummySession();
-        }
-        return $inst;
-    }
-
-    public function restart(): Session
+    public function restart(): static
     {
         $this->sessionInfo = [];
         return $this;
@@ -49,13 +39,13 @@ class DummySession extends Session
 
     }
 
-    public function setReadOnly(): Session
+    public function setReadOnly(): static
     {
         $this->writeClosed = true;
         return $this;
     }
 
-    private function set(string $name, $value)
+    protected function set(string $name, $value)
     {
         $this->sessionInfo[$name] = $value;
     }
@@ -77,52 +67,12 @@ class DummySession extends Session
         return $this->get($name);
     }
 
-    private function get(string $name)
+    protected function get(string $name)
     {
         return $this->sessionInfo[$name] ?? null;
     }
 
-    public function login(int $userID, string $userName, int $grade, bool $reqOTP, ?string $tokenValidUntil, ?int $tokenID, array $acl): Session
-    {
-        $this->set('userID', $userID);
-        $this->set('userName', $userName);
-        $this->set('ip', Util::get_client_ip(true));
-        $this->set('time', time());
-        $this->set('userGrade', $grade);
-        $this->set('acl', $acl);
-        $this->set('reqOTP', $reqOTP);
-        $this->set('tokenValidUntil', $tokenValidUntil);
-        $this->set('tokenID', $tokenID);
-        return $this;
-    }
-
-    public function setReqOTP(bool $reqOTP=false, string $tokenValidUntil){
-        $this->set('reqOTP', $reqOTP);
-        $this->set('tokenValidUntil', $tokenValidUntil);
-    }
-
-
-    public function logout(): Session
-    {
-        if ($this->writeClosed) {
-            $this->restart();
-        }
-        if (class_exists('\\sammo\\UniqueConst')) {
-            $this->logoutGame();
-        }
-
-        $this->set('userID', null);
-        $this->set('userName', null);
-        $this->set('userGrade', null);
-        $this->set('acl', null);
-        $this->set('reqOTP', null);
-        $this->set('time', time());
-        $this->set('lastMsgGet', null);
-        $this->set('tokenID', null);
-        return $this;
-    }
-
-    public function loginGame(&$result = null): Session
+    public function loginGame(&$result = null): static
     {
         $userID = $this->userID;
         if (!$userID) {
@@ -173,96 +123,6 @@ class DummySession extends Session
         return $this;
     }
 
-    public function logoutGame(): Session
-    {
-        if ($this->writeClosed) {
-            $this->restart();
-        }
-        $serverID = UniqueConst::$serverID;
-        $this->set($serverID.static::GAME_KEY_DATE, null);
-        $this->set($serverID.static::GAME_KEY_GENERAL_ID, null);
-        $this->set($serverID.static::GAME_KEY_GENERAL_NAME, null);
-        $this->set($serverID.static::GAME_KEY_EXPECTED_DEADTIME, null);
-        return $this;
-    }
-
-
-    /**
-     * 로그인 유저의 전역 grade를 받아옴
-     * @return int|null
-     */
-    public static function getUserGrade(bool $requireLogin = false, string $exitPath = '..')
-    {
-        if ($requireLogin) {
-            $obj = self::requireLogin($exitPath);
-        } else {
-            $obj = self::getInstance();
-        }
-
-        return $obj->userGrade;
-    }
-
-    /**
-     * 로그인한 유저의 전역 id(숫자)를 받아옴
-     *
-     * @return int|null
-     */
-    public static function getUserID(bool $requireLogin = false, string $exitPath = '..')
-    {
-        if ($requireLogin) {
-            $obj = self::requireLogin($exitPath);
-        } else {
-            $obj = self::getInstance();
-        }
-
-        return $obj->userID;
-    }
-
-    /**
-     *
-     */
-    public static function getGeneralID(bool $requireLogin = false, string $exitPath = '..')
-    {
-        if ($requireLogin) {
-            $obj = self::requireLogin($exitPath);
-        } else {
-            $obj = self::getInstance();
-        }
-
-        return $obj->generalID??0;
-    }
-
-    public function isLoggedIn(bool $ignoreOTP = false): bool
-    {
-        if(!$ignoreOTP){
-            if($this->reqOTP){
-                return false;
-            }
-            if(!$this->tokenValidUntil){
-                return false;
-            }
-            $now = TimeUtil::now();
-            if($this->tokenValidUntil < $now){
-                return false;
-            }
-        }
-
-        if ($this->userID) {
-            return true;
-        } else {
-            return false;
-        }
-    }
-
-    public function isGameLoggedIn(): bool
-    {
-        if ($this->generalID) {
-            return true;
-        } else {
-            return false;
-        }
-    }
-
     public function __destruct()
     {
     }
diff --git a/src/sammo/Session.php b/src/sammo/Session.php
index 02cf7c2a..305f0f87 100644
--- a/src/sammo/Session.php
+++ b/src/sammo/Session.php
@@ -38,19 +38,20 @@ class Session
     const GAME_KEY_EXPECTED_DEADTIME = '_g_deadtime';
 
 
-    private $writeClosed = false;
+    protected $writeClosed = false;
     private $sessionID = null;
 
-    public static function getInstance(): Session
+    protected static $instance = null;
+
+    public static function getInstance(): static
     {
-        static $inst = null;
-        if ($inst === null) {
-            $inst = new Session();
+        if (static::$instance === null) {
+            static::$instance = new static();
         }
-        return $inst;
+        return static::$instance;
     }
 
-    public function restart(): Session
+    public function restart(): static
     {
         //NOTE: logout 프로세스는 아예 세션을 날려버리기도 하므로, 항상 안전하게 session_restart가 가능함을 보장하지 않음.
         ini_set('session.use_only_cookies', 'false');
@@ -82,7 +83,7 @@ class Session
         Json::die($result + $jsonResult);
     }
 
-    public static function requireLogin($actionOnError = '..'): Session
+    public static function requireLogin($actionOnError = '..'): static
     {
         $session = static::getInstance();
         if ($session->isLoggedIn()) {
@@ -92,7 +93,7 @@ class Session
         static::die($actionOnError);
     }
 
-    public static function requireGameLogin($actionOnError = '..'): Session
+    public static function requireGameLogin($actionOnError = '..'): static
     {
         $session = static::requireLogin($actionOnError)->loginGame();
 
@@ -121,7 +122,7 @@ class Session
         }
     }
 
-    public function setReadOnly(): Session
+    public function setReadOnly(): static
     {
         if (!$this->writeClosed) {
             session_write_close();
@@ -132,7 +133,7 @@ class Session
 
     public function __set(string $name, $value)
     {
-        if (key_exists($name, self::PROTECTED_NAMES)) {
+        if (key_exists($name, static::PROTECTED_NAMES)) {
             trigger_error("{$name}은 외부에서 쓰기 금지된 Session 변수입니다.", E_USER_NOTICE);
             return;
         }
@@ -140,7 +141,7 @@ class Session
         $this->set($name, $value);
     }
 
-    private function set(string $name, $value)
+    protected function set(string $name, $value)
     {
         if ($value === null) {
             unset($_SESSION[$name]);
@@ -166,12 +167,12 @@ class Session
         return $this->get($name);
     }
 
-    private function get(string $name)
+    protected function get(string $name)
     {
         return Util::array_get($_SESSION[$name]);
     }
 
-    public function login(int $userID, string $userName, int $grade, bool $reqOTP, ?string $tokenValidUntil, ?int $tokenID, array $acl): Session
+    public function login(int $userID, string $userName, int $grade, bool $reqOTP, ?string $tokenValidUntil, ?int $tokenID, array $acl): static
     {
         $this->set('userID', $userID);
         $this->set('userName', $userName);
@@ -191,7 +192,7 @@ class Session
     }
 
 
-    public function logout(): Session
+    public function logout(): static
     {
         if ($this->writeClosed) {
             $this->restart();
@@ -214,7 +215,7 @@ class Session
         return $this;
     }
 
-    public function loginGame(&$result = null): Session
+    public function loginGame(&$result = null): static
     {
         $userID = $this->userID;
         if (!$userID) {
@@ -300,7 +301,7 @@ class Session
         return $this;
     }
 
-    public function logoutGame(): Session
+    public function logoutGame(): static
     {
         if ($this->writeClosed) {
             $this->restart();
@@ -321,9 +322,9 @@ class Session
     public static function getUserGrade(bool $requireLogin = false, string $exitPath = '..')
     {
         if ($requireLogin) {
-            $obj = self::requireLogin($exitPath);
+            $obj = static::requireLogin($exitPath);
         } else {
-            $obj = self::getInstance();
+            $obj = static::getInstance();
         }
 
         return $obj->userGrade;
@@ -337,9 +338,9 @@ class Session
     public static function getUserID(bool $requireLogin = false, string $exitPath = '..')
     {
         if ($requireLogin) {
-            $obj = self::requireLogin($exitPath);
+            $obj = static::requireLogin($exitPath);
         } else {
-            $obj = self::getInstance();
+            $obj = static::getInstance();
         }
 
         return $obj->userID;
@@ -351,9 +352,9 @@ class Session
     public static function getGeneralID(bool $requireLogin = false, string $exitPath = '..')
     {
         if ($requireLogin) {
-            $obj = self::requireLogin($exitPath);
+            $obj = static::requireLogin($exitPath);
         } else {
-            $obj = self::getInstance();
+            $obj = static::getInstance();
         }
 
         return $obj->generalID??0;