diff --git a/adminfront/src/features/user-groups/routes/TenantUserGroupsTab.tsx b/adminfront/src/features/user-groups/routes/TenantUserGroupsTab.tsx
index f6aa4060..8dd1f01e 100644
--- a/adminfront/src/features/user-groups/routes/TenantUserGroupsTab.tsx
+++ b/adminfront/src/features/user-groups/routes/TenantUserGroupsTab.tsx
@@ -229,7 +229,8 @@ const MemberTable: React.FC<{
   });
 
   const removeMutation = useMutation({
-    mutationFn: (userId: string) => updateUser(userId, { tenantSlug: "" }),
+    mutationFn: (userId: string) =>
+      updateUser(userId, { tenantSlug, isRemoveTenant: true }),
     onSuccess: () => {
       queryClient.invalidateQueries({ queryKey: ["tenants-full-tree-v2"] });
       toast.success(t("msg.info.saved_success", "조직에서 제외되었습니다."));
diff --git a/backend/internal/handler/user_handler.go b/backend/internal/handler/user_handler.go
index 8502e096..587e4cf0 100644
--- a/backend/internal/handler/user_handler.go
+++ b/backend/internal/handler/user_handler.go
@@ -1588,27 +1588,54 @@ func (h *UserHandler) UpdateUser(c *fiber.Ctx) error {
 				}
 			}
 		} else {
-			// Normal update: replace primary company code and ensure it's in existingCodes
-			traits["companyCode"] = code
-			// Resolve TenantID for Kratos Trait
-			if h.TenantService != nil && code != "" {
-				if tenant, err := h.TenantService.GetTenantBySlug(c.Context(), code); err == nil && tenant != nil {
-					traits["tenant_id"] = tenant.ID
-				}
-			}
+		        // Normal update (Move): replace primary company code and remove the old one from existingCodes
+		        currentPrimary := extractTraitString(traits, "companyCode")
+		        if currentPrimary != "" && currentPrimary != code {
+		                // Remove old primary from existingCodes
+		                var newCodes []string
+		                for _, existing := range existingCodes {
+		                        if existing != currentPrimary {
+		                                newCodes = append(newCodes, existing)
+		                        }
+		                }
+		                existingCodes = newCodes
 
-			found := false
-			for _, existing := range existingCodes {
-				if existing == code {
-					found = true
-					break
-				}
-			}
-			if !found && code != "" {
-				existingCodes = append(existingCodes, code)
-			}
-		}
-	}
+		                // [Keto Sync] Remove membership for the old tenant
+		                if h.TenantService != nil && h.KetoOutboxRepo != nil {
+		                        go func(removedSlug string) {
+		                                bgCtx := context.Background()
+		                                if t, err := h.TenantService.GetTenantBySlug(bgCtx, removedSlug); err == nil && t != nil {
+		                                        _ = h.KetoOutboxRepo.Create(bgCtx, &domain.KetoOutbox{
+		                                                Namespace: "Tenant",
+		                                                Object:    t.ID,
+		                                                Relation:  "members",
+		                                                Subject:   "User:" + userID,
+		                                                Action:    domain.KetoOutboxActionDelete,
+		                                        })
+		                                }
+		                        }(currentPrimary)
+		                }
+		        }
+
+		        traits["companyCode"] = code
+		        // Resolve TenantID for Kratos Trait
+		        if h.TenantService != nil && code != "" {
+		                if tenant, err := h.TenantService.GetTenantBySlug(c.Context(), code); err == nil && tenant != nil {
+		                        traits["tenant_id"] = tenant.ID
+		                }
+		        }
+
+		        found := false
+		        for _, existing := range existingCodes {
+		                if existing == code {
+		                        found = true
+		                        break
+		                }
+		        }
+		        if !found && code != "" {
+		                existingCodes = append(existingCodes, code)
+		        }
+		}	}
 
 	// Deduplicate and save back companyCodes
 	var codesToSave []string