diff --git a/docs/development/current/main/core_boxes_design.md b/docs/development/current/main/core_boxes_design.md
index d9a28cf6..fedd1062 100644
--- a/docs/development/current/main/core_boxes_design.md
+++ b/docs/development/current/main/core_boxes_design.md
@@ -884,3 +884,231 @@ fn test_console_service_ring0_integration() {
 - IntegerService/BoolService 実装（純粋関数で実装）
 - 代表パス拡大（5-10箇所）
 - #[allow(dead_code)] 完全撲滅
+
+---
+
+## 13. Phase 96: ArrayService/MapService 実装 (2025-12-03)
+
+### 13.1 実装成果
+
+**完了項目**:
+- ✅ ArrayService trait 定義（len/get/set/push）
+- ✅ MapService trait 定義（size/has/get/set）
+- ✅ ArrayBoxAdapter/MapBoxAdapter unit struct 化
+- ✅ downcast パターンで複数インスタンス対応
+- ✅ #[allow(dead_code)] 完全削除（4箇所 → 2箇所）
+
+### 13.2 Adapter パターン完成
+
+**3つのパターン確立**:
+
+1. **Ring0直結型**（ConsoleService）
+   - OS API thin wrapper
+   - Box 状態不要
+   - Ring0Context 経由でシステムコール
+
+2. **純粋関数型**（StringService）
+   - 副作用なし
+   - Box 状態不要
+   - 入力のみから出力を決定
+
+3. **downcast型**（ArrayService/MapService）
+   - 複数インスタンス対応
+   - Box 状態が必要
+   - unit struct + downcast パターン
+
+### 13.3 ArrayService API
+
+**Trait 定義**:
+```rust
+pub trait ArrayService: Send + Sync {
+    /// 配列の要素数を取得
+    fn len(&self, arr: &dyn NyashBox) -> i64;
+
+    /// 指定インデックスの要素を取得
+    fn get(&self, arr: &dyn NyashBox, index: i64) -> Option<Box<dyn NyashBox>>;
+
+    /// 指定インデックスに要素を設定
+    fn set(&self, arr: &dyn NyashBox, index: i64, value: Box<dyn NyashBox>) -> Result<(), String>;
+
+    /// 配列の末尾に要素を追加
+    fn push(&self, arr: &dyn NyashBox, value: Box<dyn NyashBox>) -> Result<(), String>;
+}
+```
+
+**実装例**:
+```rust
+impl ArrayService for ArrayBoxAdapter {
+    fn len(&self, arr: &dyn NyashBox) -> i64 {
+        arr.as_any()
+           .downcast_ref::<ArrayBox>()
+           .map(|a| a.len() as i64)
+           .unwrap_or(0)
+    }
+
+    fn get(&self, arr: &dyn NyashBox, index: i64) -> Option<Box<dyn NyashBox>> {
+        let arr_box = arr.as_any().downcast_ref::<ArrayBox>()?;
+        let index_box = Box::new(IntegerBox::new(index));
+        Some(arr_box.get(index_box))
+    }
+
+    // set/push も同様の downcast パターン
+}
+```
+
+### 13.4 MapService API
+
+**Trait 定義**:
+```rust
+pub trait MapService: Send + Sync {
+    /// マップのサイズを取得
+    fn size(&self, map: &dyn NyashBox) -> i64;
+
+    /// キーが存在するか確認
+    fn has(&self, map: &dyn NyashBox, key: &str) -> bool;
+
+    /// 値を取得
+    fn get(&self, map: &dyn NyashBox, key: &str) -> Option<Box<dyn NyashBox>>;
+
+    /// 値を設定
+    fn set(&self, map: &dyn NyashBox, key: &str, value: Box<dyn NyashBox>) -> Result<(), String>;
+}
+```
+
+**実装例**:
+```rust
+impl MapService for MapBoxAdapter {
+    fn size(&self, map: &dyn NyashBox) -> i64 {
+        map.as_any()
+           .downcast_ref::<MapBox>()
+           .map(|m| {
+               let size_box = m.size();
+               size_box.as_any()
+                   .downcast_ref::<IntegerBox>()
+                   .map(|i| i.value)
+                   .unwrap_or(0)
+           })
+           .unwrap_or(0)
+    }
+
+    fn has(&self, map: &dyn NyashBox, key: &str) -> bool {
+        let map_box = match map.as_any().downcast_ref::<MapBox>() {
+            Some(m) => m,
+            None => return false,
+        };
+        let key_box = Box::new(StringBox::new(key));
+        let result = map_box.has(key_box);
+        result.as_any()
+              .downcast_ref::<BoolBox>()
+              .map(|b| b.value)
+              .unwrap_or(false)
+    }
+
+    // get/set も同様の downcast パターン
+}
+```
+
+### 13.5 PluginHost 初期化更新
+
+**Phase 95.5 パターンを踏襲**:
+```rust
+// ArrayBox (Phase 96: downcast パターン、存在チェックのみ)
+if !registry.has_type("ArrayBox") {
+    return Err(CoreInitError::MissingService {
+        box_id: CoreBoxId::Array,
+        message: "ArrayBox not found in registry".to_string(),
+    });
+}
+let array_service = Arc::new(ArrayBoxAdapter::new());
+
+// MapBox (Phase 96: downcast パターン、存在チェックのみ)
+if !registry.has_type("MapBox") {
+    return Err(CoreInitError::MissingService {
+        box_id: CoreBoxId::Map,
+        message: "MapBox not found in registry".to_string(),
+    });
+}
+let map_service = Arc::new(MapBoxAdapter::new());
+```
+
+### 13.6 テスト追加
+
+**ArrayService テスト**:
+```rust
+#[test]
+fn test_array_service_basic_operations() {
+    let arr = ArrayBox::new();
+    let adapter = ArrayBoxAdapter::new();
+
+    // push
+    let value = Box::new(IntegerBox::new(42));
+    adapter.push(&arr, value).unwrap();
+
+    // len
+    assert_eq!(adapter.len(&arr), 1);
+
+    // get
+    let result = adapter.get(&arr, 0).unwrap();
+    let int_box = result.as_any().downcast_ref::<IntegerBox>().unwrap();
+    assert_eq!(int_box.value, 42);
+}
+```
+
+**MapService テスト**:
+```rust
+#[test]
+fn test_map_service_basic_operations() {
+    let map = MapBox::new();
+    let adapter = MapBoxAdapter::new();
+
+    // set
+    let value = Box::new(StringBox::new("Hello"));
+    adapter.set(&map, "key1", value).unwrap();
+
+    // has
+    assert!(adapter.has(&map, "key1"));
+    assert!(!adapter.has(&map, "key2"));
+
+    // get
+    let result = adapter.get(&map, "key1").unwrap();
+    let str_box = result.as_any().downcast_ref::<StringBox>().unwrap();
+    assert_eq!(str_box.value, "Hello");
+
+    // size
+    assert_eq!(adapter.size(&map), 1);
+}
+```
+
+### 13.7 削減統計
+
+| 項目 | Before | After | 削減 |
+|------|--------|-------|------|
+| #[allow(dead_code)] | 4箇所 | 2箇所 | 2削減 |
+| inner フィールド | 4個 | 2個 | 2削減 |
+| Box 依存 | 4箇所 | 2箇所 | 2削減 |
+
+**残存 Adapter**:
+- IntegerBoxAdapter: Phase 97 で実装予定
+- BoolBoxAdapter: Phase 97 で実装予定
+
+### 13.8 技術的成果
+
+**型安全性向上**:
+- downcast_ref によるコンパイル時検証
+- Option/Result による安全なエラーハンドリング
+- Box<dyn NyashBox> ↔ Rust型 の明示的変換
+
+**コード簡略化**:
+- unit struct 化により inner フィールド削除
+- #[allow(dead_code)] 完全削除（2箇所削減）
+- 存在チェックのみのシンプルな初期化
+
+**設計明確化**:
+- 3パターンの使い分け確立
+- Adapter の責務明確化（複数インスタンス対応）
+
+### 13.9 次のステップ（Phase 97）
+
+- IntegerService/BoolService 実装（純粋関数型で実装）
+- 代表パス拡大（5-10箇所で実用化テスト）
+- #[allow(dead_code)] 完全撲滅（0箇所達成）
diff --git a/src/runtime/core_services.rs b/src/runtime/core_services.rs
index a8cb2649..278154e9 100644
--- a/src/runtime/core_services.rs
+++ b/src/runtime/core_services.rs
@@ -25,13 +25,37 @@ pub trait BoolService: Send + Sync {
 }
 
 /// ArrayBox Service trait
+///
+/// Phase 96: len/get/set/push 実装
 pub trait ArrayService: Send + Sync {
-    // Phase 92 以降で実装
+    /// 配列の要素数を取得
+    fn len(&self, arr: &dyn NyashBox) -> i64;
+
+    /// 指定インデックスの要素を取得
+    fn get(&self, arr: &dyn NyashBox, index: i64) -> Option<Box<dyn NyashBox>>;
+
+    /// 指定インデックスに要素を設定
+    fn set(&self, arr: &dyn NyashBox, index: i64, value: Box<dyn NyashBox>) -> Result<(), String>;
+
+    /// 配列の末尾に要素を追加
+    fn push(&self, arr: &dyn NyashBox, value: Box<dyn NyashBox>) -> Result<(), String>;
 }
 
 /// MapBox Service trait
+///
+/// Phase 96: size/has/get/set 実装
 pub trait MapService: Send + Sync {
-    // Phase 92 以降で実装
+    /// マップのサイズを取得
+    fn size(&self, map: &dyn NyashBox) -> i64;
+
+    /// キーが存在するか確認
+    fn has(&self, map: &dyn NyashBox, key: &str) -> bool;
+
+    /// 値を取得
+    fn get(&self, map: &dyn NyashBox, key: &str) -> Option<Box<dyn NyashBox>>;
+
+    /// 値を設定
+    fn set(&self, map: &dyn NyashBox, key: &str, value: Box<dyn NyashBox>) -> Result<(), String>;
 }
 
 /// ConsoleBox Service trait
@@ -166,40 +190,113 @@ impl BoolService for BoolBoxAdapter {
 
 /// ArrayBox → ArrayService Adapter
 ///
-/// Phase 95.5: inner フィールドは #[allow(dead_code)] のまま保持
-/// Phase 96 以降で実装時に、Box 状態が必要か純粋関数で足りるか判断
-pub struct ArrayBoxAdapter {
-    #[allow(dead_code)]
-    inner: Box<dyn NyashBox>,
-}
+/// Phase 96: downcast パターンで複数インスタンス対応
+pub struct ArrayBoxAdapter;
 
 impl ArrayBoxAdapter {
-    pub fn new(box_instance: Box<dyn NyashBox>) -> Self {
-        Self { inner: box_instance }
+    pub fn new() -> Self {
+        Self
     }
 }
 
 impl ArrayService for ArrayBoxAdapter {
-    // Phase 96 以降で実装
+    fn len(&self, arr: &dyn NyashBox) -> i64 {
+        use crate::boxes::array::ArrayBox;
+        arr.as_any()
+           .downcast_ref::<ArrayBox>()
+           .map(|a| a.len() as i64)
+           .unwrap_or(0)
+    }
+
+    fn get(&self, arr: &dyn NyashBox, index: i64) -> Option<Box<dyn NyashBox>> {
+        use crate::boxes::array::ArrayBox;
+        use crate::box_trait::IntegerBox;
+        let arr_box = arr.as_any().downcast_ref::<ArrayBox>()?;
+        let index_box = Box::new(IntegerBox::new(index));
+        Some(arr_box.get(index_box))
+    }
+
+    fn set(&self, arr: &dyn NyashBox, index: i64, value: Box<dyn NyashBox>) -> Result<(), String> {
+        use crate::boxes::array::ArrayBox;
+        use crate::box_trait::IntegerBox;
+        let arr_box = arr.as_any()
+            .downcast_ref::<ArrayBox>()
+            .ok_or("Not an ArrayBox")?;
+        let index_box = Box::new(IntegerBox::new(index));
+        arr_box.set(index_box, value);
+        Ok(())
+    }
+
+    fn push(&self, arr: &dyn NyashBox, value: Box<dyn NyashBox>) -> Result<(), String> {
+        use crate::boxes::array::ArrayBox;
+        let arr_box = arr.as_any()
+            .downcast_ref::<ArrayBox>()
+            .ok_or("Not an ArrayBox")?;
+        arr_box.push(value);
+        Ok(())
+    }
 }
 
 /// MapBox → MapService Adapter
 ///
-/// Phase 95.5: inner フィールドは #[allow(dead_code)] のまま保持
-/// Phase 96 以降で実装時に、Box 状態が必要か純粋関数で足りるか判断
-pub struct MapBoxAdapter {
-    #[allow(dead_code)]
-    inner: Box<dyn NyashBox>,
-}
+/// Phase 96: downcast パターンで複数インスタンス対応
+pub struct MapBoxAdapter;
 
 impl MapBoxAdapter {
-    pub fn new(box_instance: Box<dyn NyashBox>) -> Self {
-        Self { inner: box_instance }
+    pub fn new() -> Self {
+        Self
     }
 }
 
 impl MapService for MapBoxAdapter {
-    // Phase 96 以降で実装
+    fn size(&self, map: &dyn NyashBox) -> i64 {
+        use crate::boxes::map_box::MapBox;
+        map.as_any()
+           .downcast_ref::<MapBox>()
+           .map(|m| {
+               // MapBox::size() は Box<dyn NyashBox> を返すため、IntegerBox に変換
+               let size_box = m.size();
+               size_box.as_any()
+                   .downcast_ref::<crate::box_trait::IntegerBox>()
+                   .map(|i| i.value)
+                   .unwrap_or(0)
+           })
+           .unwrap_or(0)
+    }
+
+    fn has(&self, map: &dyn NyashBox, key: &str) -> bool {
+        use crate::boxes::map_box::MapBox;
+        use crate::box_trait::{BoolBox, StringBox};
+        let map_box = match map.as_any().downcast_ref::<MapBox>() {
+            Some(m) => m,
+            None => return false,
+        };
+        let key_box = Box::new(StringBox::new(key));
+        let result = map_box.has(key_box);
+        result.as_any()
+              .downcast_ref::<BoolBox>()
+              .map(|b| b.value)
+              .unwrap_or(false)
+    }
+
+    fn get(&self, map: &dyn NyashBox, key: &str) -> Option<Box<dyn NyashBox>> {
+        use crate::boxes::map_box::MapBox;
+        use crate::box_trait::StringBox;
+        let map_box = map.as_any().downcast_ref::<MapBox>()?;
+        let key_box = Box::new(StringBox::new(key));
+        Some(map_box.get(key_box))
+    }
+
+    fn set(&self, map: &dyn NyashBox, key: &str, value: Box<dyn NyashBox>) -> Result<(), String> {
+        use crate::boxes::map_box::MapBox;
+        use crate::box_trait::StringBox;
+        let map_box = map.as_any()
+            .downcast_ref::<MapBox>()
+            .ok_or("Not a MapBox")?;
+        let key_box = Box::new(StringBox::new(key));
+        map_box.set(key_box, value);
+        Ok(())
+    }
 }
 
 /// ConsoleBox → ConsoleService Adapter
@@ -317,4 +414,95 @@ mod tests {
 
         // panic しないことを確認
     }
+
+    #[test]
+    fn test_array_service_basic_operations() {
+        use crate::boxes::array::ArrayBox;
+        use crate::box_trait::IntegerBox;
+
+        let arr = ArrayBox::new();
+        let adapter = ArrayBoxAdapter::new();
+
+        // push
+        let value = Box::new(IntegerBox::new(42));
+        adapter.push(&arr, value).unwrap();
+
+        // len
+        assert_eq!(adapter.len(&arr), 1);
+
+        // get
+        let result = adapter.get(&arr, 0).unwrap();
+        let int_box = result.as_any().downcast_ref::<IntegerBox>().unwrap();
+        assert_eq!(int_box.value, 42);
+    }
+
+    #[test]
+    fn test_array_service_set() {
+        use crate::boxes::array::ArrayBox;
+        use crate::box_trait::IntegerBox;
+
+        let arr = ArrayBox::new();
+        let adapter = ArrayBoxAdapter::new();
+
+        // push initial value
+        adapter.push(&arr, Box::new(IntegerBox::new(10))).unwrap();
+
+        // set
+        adapter.set(&arr, 0, Box::new(IntegerBox::new(20))).unwrap();
+
+        // verify
+        let result = adapter.get(&arr, 0).unwrap();
+        let int_box = result.as_any().downcast_ref::<IntegerBox>().unwrap();
+        assert_eq!(int_box.value, 20);
+    }
+
+    #[test]
+    fn test_map_service_basic_operations() {
+        use crate::boxes::map_box::MapBox;
+        use crate::box_trait::StringBox;
+
+        let map = MapBox::new();
+        let adapter = MapBoxAdapter::new();
+
+        // set
+        let value = Box::new(StringBox::new("Hello"));
+        adapter.set(&map, "key1", value).unwrap();
+
+        // has
+        assert!(adapter.has(&map, "key1"));
+        assert!(!adapter.has(&map, "key2"));
+
+        // get
+        let result = adapter.get(&map, "key1").unwrap();
+        let str_box = result.as_any().downcast_ref::<StringBox>().unwrap();
+        assert_eq!(str_box.value, "Hello");
+
+        // size
+        assert_eq!(adapter.size(&map), 1);
+    }
+
+    #[test]
+    fn test_map_service_multiple_keys() {
+        use crate::boxes::map_box::MapBox;
+        use crate::box_trait::{IntegerBox, StringBox};
+
+        let map = MapBox::new();
+        let adapter = MapBoxAdapter::new();
+
+        // set multiple keys
+        adapter.set(&map, "name", Box::new(StringBox::new("Alice"))).unwrap();
+        adapter.set(&map, "age", Box::new(IntegerBox::new(25))).unwrap();
+
+        // verify size
+        assert_eq!(adapter.size(&map), 2);
+
+        // verify values
+        let name = adapter.get(&map, "name").unwrap();
+        let name_str = name.as_any().downcast_ref::<StringBox>().unwrap();
+        assert_eq!(name_str.value, "Alice");
+
+        let age = adapter.get(&map, "age").unwrap();
+        let age_int = age.as_any().downcast_ref::<IntegerBox>().unwrap();
+        assert_eq!(age_int.value, 25);
+    }
 }
diff --git a/src/runtime/plugin_host.rs b/src/runtime/plugin_host.rs
index 51593de5..424bd69a 100644
--- a/src/runtime/plugin_host.rs
+++ b/src/runtime/plugin_host.rs
@@ -127,23 +127,23 @@ impl PluginHost {
             })?;
         let bool_service = Arc::new(BoolBoxAdapter::new(bool_box));
 
-        // ArrayBox
-        let array_box = registry
-            .create_box("ArrayBox", &[])
-            .map_err(|e| CoreInitError::MissingService {
+        // ArrayBox (Phase 96: downcast パターン、存在チェックのみ)
+        if !registry.has_type("ArrayBox") {
+            return Err(CoreInitError::MissingService {
                 box_id: CoreBoxId::Array,
-                message: format!("ArrayBox creation failed: {}", e),
-            })?;
-        let array_service = Arc::new(ArrayBoxAdapter::new(array_box));
+                message: "ArrayBox not found in registry".to_string(),
+            });
+        }
+        let array_service = Arc::new(ArrayBoxAdapter::new());
 
-        // MapBox
-        let map_box = registry
-            .create_box("MapBox", &[])
-            .map_err(|e| CoreInitError::MissingService {
+        // MapBox (Phase 96: downcast パターン、存在チェックのみ)
+        if !registry.has_type("MapBox") {
+            return Err(CoreInitError::MissingService {
                 box_id: CoreBoxId::Map,
-                message: format!("MapBox creation failed: {}", e),
-            })?;
-        let map_service = Arc::new(MapBoxAdapter::new(map_box));
+                message: "MapBox not found in registry".to_string(),
+            });
+        }
+        let map_service = Arc::new(MapBoxAdapter::new());
 
         // ConsoleBox (Phase 95.5: Ring0 直結、存在チェックのみ)
         if !registry.has_type("ConsoleBox") {