diff --git a/Assets/Scripts/Mechanics/PlayerController.cs b/Assets/Scripts/Mechanics/PlayerController.cs
index cbfccdc..5fc89c7 100644
--- a/Assets/Scripts/Mechanics/PlayerController.cs
+++ b/Assets/Scripts/Mechanics/PlayerController.cs
@@ -41,6 +41,11 @@ namespace Platformer.Mechanics
 
         public JumpState jumpState = JumpState.Grounded;
         private bool stopJump;
+
+        // BT69 — Down + Jump Drop-Through (PD 명시 2026-05-08): Down 누른 상태에서 점프 시 발판 통과 + 점프 모션
+        private float dropThroughTimer = 0f;  // 활성 시간 동안 Layer 16 mask 강제 OFF
+        private const float DROP_THROUGH_DURATION = 0.3f;  // Drop-Through 활성 지속 시간 (초)
+        private bool dropThroughJump = false;  // 본 frame Drop-Through 점프 발동 여부 (velocity.y 처리 분기)
         /*internal new*/ public Collider2D collider2d;
         /*internal new*/ public AudioSource audioSource;
         public Health health;
@@ -136,9 +141,19 @@ namespace Platformer.Mechanics
         {
             if (controlEnabled)
             {
-                move.x = m_MoveAction.ReadValue<Vector2>().x;
+                Vector2 moveInput = m_MoveAction.ReadValue<Vector2>();
+                move.x = moveInput.x;
                 if (jumpState == JumpState.Grounded && m_JumpAction.WasPressedThisFrame())
+                {
+                    // BT69 — Down + Jump = Drop-Through (PD 명시 2026-05-08)
+                    bool downHeld = moveInput.y < -0.5f;
+                    if (downHeld)
+                    {
+                        dropThroughTimer = DROP_THROUGH_DURATION;
+                        dropThroughJump = true;
+                    }
                     jumpState = JumpState.PrepareToJump;
+                }
                 else if (m_JumpAction.WasReleasedThisFrame())
                 {
                     stopJump = true;
@@ -150,6 +165,9 @@ namespace Platformer.Mechanics
             {
                 move.x = 0;
             }
+
+            // BT69 — Drop-Through Timer 감소 (Layer 16 mask 강제 OFF 지속 시간)
+            if (dropThroughTimer > 0f) dropThroughTimer -= Time.deltaTime;
             UpdateJumpState();
             base.Update();
 
@@ -205,8 +223,10 @@ namespace Platformer.Mechanics
             int baseMask = Physics2D.GetLayerCollisionMask(gameObject.layer);
 
             // BT5-Dev #43 — IsGrounded 영역 폐기 (frame 0 미설정 → 떨어짐). footHit 단독 + 점프 영역 OFF 강제
+            // BT69 — Drop-Through Timer 활성 시 Layer 16 mask 강제 OFF (Down + Jump 입력 발판 통과)
             bool isJumpingThrough = jumpState == JumpState.Jumping
-                                    || (jumpState == JumpState.InFlight && velocity.y > 0.01f);
+                                    || (jumpState == JumpState.InFlight && velocity.y > 0.01f)
+                                    || dropThroughTimer > 0f;
 
             bool standingOnPlatform = false;
             if (collider2d != null && !isJumpingThrough)
@@ -227,7 +247,16 @@ namespace Platformer.Mechanics
         {
             if (jump && IsGrounded)
             {
-                velocity.y = jumpTakeOffSpeed * model.jumpModifier;
+                // BT69 — Drop-Through 점프 분기: Down + Jump 입력 시 위로 점프 X (gravity로 떨어짐 + 점프 모션만 유지)
+                if (dropThroughJump)
+                {
+                    velocity.y = 0f;  // 위 속도 X — 발판 통과 후 자연 낙하
+                    dropThroughJump = false;
+                }
+                else
+                {
+                    velocity.y = jumpTakeOffSpeed * model.jumpModifier;
+                }
                 jump = false;
             }
             else if (stopJump)