diff --git a/core/group_party.go b/core/group_party.go
index b50f530..abe3660 100644
--- a/core/group_party.go
+++ b/core/group_party.go
@@ -176,16 +176,22 @@ func (gd *partyDoc) addInvite(mid accountID, body bson.M, ttl time.Duration, max
 	return newdoc, err
 }
 
-func (gd *partyDoc) addMember(mid accountID, character bson.M) (bson.M, error) {
+func (gd *partyDoc) addMember(mid accountID, character bson.M, option string) (bson.M, error) {
 	tid := gd.tid(mid)
 	prefix := "$._members." + tid
 
-	if _, err := gd.rh.JSONSet(gd.strid(), prefix+"._body", character, gocommon.RedisonSetOptionXX); err != nil {
-		return nil, err
-	}
+	if option == gocommon.RedisonSetOptionNX {
+		if _, err := gd.rh.JSONSet(gd.strid(), prefix, bson.M{"_body": character}, gocommon.RedisonSetOptionNX); err != nil {
+			return nil, err
+		}
+	} else {
+		if _, err := gd.rh.JSONSet(gd.strid(), prefix+"._body", character, gocommon.RedisonSetOptionXX); err != nil {
+			return nil, err
+		}
 
-	if err := gd.rh.JSONMDel(gd.strid(), []string{prefix + "._invite", prefix + "._invite_exp"}); err != nil {
-		return nil, err
+		if err := gd.rh.JSONMDel(gd.strid(), []string{prefix + "._invite", prefix + "._invite_exp"}); err != nil {
+			return nil, err
+		}
 	}
 	gd.rh.Persist(gd.rh.Context(), gd.strid()).Result()
 
@@ -276,6 +282,7 @@ func (gp *groupParty) Initialize(tv *Tavern, cfg configDocument) error {
 		tv.wsh.EnterRoom(gid.Hex(), accid)
 	}
 	gp.leaveRoom = func(gid groupID, accid accountID) {
+		gp.rh.JSONDel(accid.Hex(), "$.party.state")
 		tv.wsh.LeaveRoom(gid.Hex(), accid)
 	}
 
@@ -291,8 +298,8 @@ func (gp *groupParty) JoinParty(w http.ResponseWriter, r *http.Request) {
 	var data struct {
 		Gid       primitive.ObjectID
 		Mid       primitive.ObjectID
-		First     bool
 		Character bson.M
+		Option    string
 	}
 	if err := gocommon.MakeDecoder(r).Decode(&data); err != nil {
 		logger.Println("JoinParty failed. DecodeGob returns err :", err)
@@ -300,9 +307,12 @@ func (gp *groupParty) JoinParty(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	// Option : ["NX" | "XX" | ""]
+
 	character := data.Character
 	gid := data.Gid
 	mid := data.Mid
+	option := strings.ToUpper(data.Option)
 
 	if gid.IsZero() || mid.IsZero() {
 		logger.Println("JoinParty failed. mid should be exist")
@@ -323,7 +333,7 @@ func (gp *groupParty) JoinParty(w http.ResponseWriter, r *http.Request) {
 	}
 
 	// 내 정보 업데이트할 때에도 사용됨
-	if !data.First {
+	if option == "XX" {
 		// 이미 멤버여야 재입장 가능
 		path := "$._members." + gd.tid(mid) + "._body"
 		if _, err := gd.rh.JSONSet(gd.strid(), path, character, gocommon.RedisonSetOptionXX); err != nil {
@@ -334,7 +344,7 @@ func (gp *groupParty) JoinParty(w http.ResponseWriter, r *http.Request) {
 	}
 
 	gp.rh.JSONSet(mid.Hex(), "$.party", bson.M{"id": gid.Hex()})
-	memdoc, err := gd.addMember(mid, character)
+	memdoc, err := gd.addMember(mid, character, option)
 	if err != nil {
 		logger.Println("JoinParty failed :", err)
 		w.WriteHeader(http.StatusInternalServerError)
@@ -361,6 +371,26 @@ func (gp *groupParty) JoinParty(w http.ResponseWriter, r *http.Request) {
 	gocommon.MakeEncoder(w, r).Encode(gd.strid())
 }
 
+func (gp *groupParty) ForceClearPartyMember(w http.ResponseWriter, r *http.Request) {
+	var doc struct {
+		Gid primitive.ObjectID
+		Mid primitive.ObjectID
+	}
+
+	if err := gocommon.MakeDecoder(r).Decode(&doc); err != nil {
+		logger.Println("ConditionalClearPartyMember failed. DecodeGob returns err :", err)
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+
+	gd := partyDoc{
+		id: doc.Gid,
+		rh: gp.rh,
+	}
+
+	gd.removeMember(doc.Mid)
+}
+
 func (gp *groupParty) ConditionalClearPartyMember(w http.ResponseWriter, r *http.Request) {
 	var doc struct {
 		Gid string
@@ -604,7 +634,7 @@ func (gp *groupParty) AcceptPartyInvitation(w http.ResponseWriter, r *http.Reque
 		rh: gp.rh,
 	}
 
-	memberDoc, err := gd.addMember(mid, member)
+	memberDoc, err := gd.addMember(mid, member, "XX")
 	if err == nil {
 		// 기존 멤버에게 새 멤버를 알림
 		gp.sendUpstreamMessage(&wshandler.UpstreamMessage{