diff --git a/.github/CODEOWNERS b/.github/CODEOWNERS
index 97b27a10e301..945ed4e9000f 100644
--- a/.github/CODEOWNERS
+++ b/.github/CODEOWNERS
@@ -16,7 +16,7 @@ common/global_parameter_loader/** kenji.miyake@tier4.jp
 common/goal_distance_calculator/** taiki.tanaka@tier4.jp
 common/grid_map_utils/** maxime.clement@tier4.jp
 common/interpolation/** fumiya.watanabe@tier4.jp takayuki.murooka@tier4.jp
-common/kalman_filter/** yukihiro.saito@tier4.jp
+common/kalman_filter/** koji.minoda@tier4.jp takeshi.ishita@tier4.jp yukihiro.saito@tier4.jp
 common/motion_common/** christopherj.ho@gmail.com
 common/motion_testing/** christopherj.ho@gmail.com
 common/motion_utils/** satoshi.ota@tier4.jp taiki.tanaka@tier4.jp takayuki.murooka@tier4.jp yutaka.shimizu@tier4.jp
diff --git a/common/kalman_filter/include/kalman_filter/time_delay_kalman_filter.hpp b/common/kalman_filter/include/kalman_filter/time_delay_kalman_filter.hpp
index 5fb615647207..1a072bb43d4a 100644
--- a/common/kalman_filter/include/kalman_filter/time_delay_kalman_filter.hpp
+++ b/common/kalman_filter/include/kalman_filter/time_delay_kalman_filter.hpp
@@ -48,15 +48,13 @@ class TimeDelayKalmanFilter : public KalmanFilter
 
   /**
    * @brief get latest time estimated state
-   * @param x latest time estimated state
    */
-  void getLatestX(Eigen::MatrixXd & x);
+  Eigen::MatrixXd getLatestX() const;
 
   /**
    * @brief get latest time estimation covariance
-   * @param P latest time estimation covariance
    */
-  void getLatestP(Eigen::MatrixXd & P);
+  Eigen::MatrixXd getLatestP() const;
 
   /**
    * @brief calculate kalman filter covariance by precision model with time delay. This is mainly
diff --git a/common/kalman_filter/src/time_delay_kalman_filter.cpp b/common/kalman_filter/src/time_delay_kalman_filter.cpp
index 3c06ef25150c..24f06dbb9821 100644
--- a/common/kalman_filter/src/time_delay_kalman_filter.cpp
+++ b/common/kalman_filter/src/time_delay_kalman_filter.cpp
@@ -32,8 +32,9 @@ void TimeDelayKalmanFilter::init(
   }
 }
 
-void TimeDelayKalmanFilter::getLatestX(Eigen::MatrixXd & x) { x = x_.block(0, 0, dim_x_, 1); }
-void TimeDelayKalmanFilter::getLatestP(Eigen::MatrixXd & P) { P = P_.block(0, 0, dim_x_, dim_x_); }
+Eigen::MatrixXd TimeDelayKalmanFilter::getLatestX() const { return x_.block(0, 0, dim_x_, 1); }
+
+Eigen::MatrixXd TimeDelayKalmanFilter::getLatestP() const { return P_.block(0, 0, dim_x_, dim_x_); }
 
 bool TimeDelayKalmanFilter::predictWithDelay(
   const Eigen::MatrixXd & x_next, const Eigen::MatrixXd & A, const Eigen::MatrixXd & Q)
diff --git a/localization/ekf_localizer/src/ekf_localizer.cpp b/localization/ekf_localizer/src/ekf_localizer.cpp
index be9bba8197be..08e120631c12 100644
--- a/localization/ekf_localizer/src/ekf_localizer.cpp
+++ b/localization/ekf_localizer/src/ekf_localizer.cpp
@@ -239,8 +239,7 @@ void EKFLocalizer::timerCallback()
 void EKFLocalizer::showCurrentX()
 {
   if (show_debug_info_) {
-    Eigen::MatrixXd X(dim_x_, 1);
-    ekf_.getLatestX(X);
+    const Eigen::MatrixXd X = ekf_.getLatestX();
     DEBUG_PRINT_MAT(X.transpose());
   }
 }
@@ -415,12 +414,10 @@ void EKFLocalizer::predictKinematicsModel()
    *     [ 0, 0,                 0,                 0,             0,  1]
    */
 
-  Eigen::MatrixXd X_curr(dim_x_, 1);  // current state
-  ekf_.getLatestX(X_curr);
+  const Eigen::MatrixXd X_curr = ekf_.getLatestX();
   DEBUG_PRINT_MAT(X_curr.transpose());
 
-  Eigen::MatrixXd P_curr;
-  ekf_.getLatestP(P_curr);
+  const Eigen::MatrixXd P_curr = ekf_.getLatestP();
 
   const double dt = ekf_dt_;
 
@@ -431,8 +428,7 @@ void EKFLocalizer::predictKinematicsModel()
   ekf_.predictWithDelay(X_next, A, Q);
 
   // debug
-  Eigen::MatrixXd X_result(dim_x_, 1);
-  ekf_.getLatestX(X_result);
+  const Eigen::MatrixXd X_result = ekf_.getLatestX();
   DEBUG_PRINT_MAT(X_result.transpose());
   DEBUG_PRINT_MAT((X_result - X_curr).transpose());
 }
@@ -449,8 +445,7 @@ void EKFLocalizer::measurementUpdatePose(const geometry_msgs::msg::PoseWithCovar
         pose.header.frame_id.c_str(), pose_frame_id_.c_str()),
       2000);
   }
-  Eigen::MatrixXd X_curr(dim_x_, 1);  // current state
-  ekf_.getLatestX(X_curr);
+  const Eigen::MatrixXd X_curr = ekf_.getLatestX();
   DEBUG_PRINT_MAT(X_curr.transpose());
 
   constexpr int dim_y = 3;  // pos_x, pos_y, yaw, depending on Pose output
@@ -496,9 +491,8 @@ void EKFLocalizer::measurementUpdatePose(const geometry_msgs::msg::PoseWithCovar
   Eigen::MatrixXd y_ekf(dim_y, 1);
   y_ekf << ekf_.getXelement(delay_step * dim_x_ + IDX::X),
     ekf_.getXelement(delay_step * dim_x_ + IDX::Y), ekf_yaw;
-  Eigen::MatrixXd P_curr, P_y;
-  ekf_.getLatestP(P_curr);
-  P_y = P_curr.block(0, 0, dim_y, dim_y);
+  const Eigen::MatrixXd P_curr = ekf_.getLatestP();
+  const Eigen::MatrixXd P_y = P_curr.block(0, 0, dim_y, dim_y);
   if (!mahalanobisGate(pose_gate_dist_, y_ekf, y, P_y)) {
     warning_.warnThrottle(
       "[EKF] Pose measurement update, mahalanobis distance is over limit. ignore "
@@ -517,8 +511,7 @@ void EKFLocalizer::measurementUpdatePose(const geometry_msgs::msg::PoseWithCovar
   ekf_.updateWithDelay(y, C, R, delay_step);
 
   // debug
-  Eigen::MatrixXd X_result(dim_x_, 1);
-  ekf_.getLatestX(X_result);
+  const Eigen::MatrixXd X_result = ekf_.getLatestX();
   DEBUG_PRINT_MAT(X_result.transpose());
   DEBUG_PRINT_MAT((X_result - X_curr).transpose());
 }
@@ -535,8 +528,7 @@ void EKFLocalizer::measurementUpdateTwist(
       "twist frame_id must be base_link");
   }
 
-  Eigen::MatrixXd X_curr(dim_x_, 1);  // current state
-  ekf_.getLatestX(X_curr);
+  const Eigen::MatrixXd X_curr = ekf_.getLatestX();
   DEBUG_PRINT_MAT(X_curr.transpose());
 
   constexpr int dim_y = 2;  // vx, wz
@@ -577,9 +569,8 @@ void EKFLocalizer::measurementUpdateTwist(
   Eigen::MatrixXd y_ekf(dim_y, 1);
   y_ekf << ekf_.getXelement(delay_step * dim_x_ + IDX::VX),
     ekf_.getXelement(delay_step * dim_x_ + IDX::WZ);
-  Eigen::MatrixXd P_curr, P_y;
-  ekf_.getLatestP(P_curr);
-  P_y = P_curr.block(4, 4, dim_y, dim_y);
+  const Eigen::MatrixXd P_curr = ekf_.getLatestP();
+  const Eigen::MatrixXd P_y = P_curr.block(4, 4, dim_y, dim_y);
   if (!mahalanobisGate(twist_gate_dist_, y_ekf, y, P_y)) {
     warning_.warnThrottle(
       "[EKF] Twist measurement update, mahalanobis distance is over limit. ignore "
@@ -599,8 +590,7 @@ void EKFLocalizer::measurementUpdateTwist(
   ekf_.updateWithDelay(y, C, R, delay_step);
 
   // debug
-  Eigen::MatrixXd X_result(dim_x_, 1);
-  ekf_.getLatestX(X_result);
+  const Eigen::MatrixXd X_result = ekf_.getLatestX();
   DEBUG_PRINT_MAT(X_result.transpose());
   DEBUG_PRINT_MAT((X_result - X_curr).transpose());
 }
@@ -611,10 +601,8 @@ void EKFLocalizer::measurementUpdateTwist(
 void EKFLocalizer::publishEstimateResult()
 {
   rclcpp::Time current_time = this->now();
-  Eigen::MatrixXd X(dim_x_, 1);
-  Eigen::MatrixXd P(dim_x_, dim_x_);
-  ekf_.getLatestX(X);
-  ekf_.getLatestP(P);
+  const Eigen::MatrixXd X = ekf_.getLatestX();
+  const Eigen::MatrixXd P = ekf_.getLatestP();
 
   /* publish latest pose */
   pub_pose_->publish(current_ekf_pose_);