diff --git a/Cargo.toml b/Cargo.toml
index e695d1026..5ba302cca 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -115,7 +115,7 @@ rev = "de226a26e8e18edbdb1d6f986afe37bbbf35fbf4"
 version = "0.0.0"
 edition = "2021"
 publish = false
-rust-version = "1.81.0"
+rust-version = "1.84.0"
 license = "MIT"
 
 # min-sized-rustを元にrelease buildのサイズが小さくなるようにした
diff --git a/crates/voicevox_core/src/infer/runtimes/onnxruntime.rs b/crates/voicevox_core/src/infer/runtimes/onnxruntime.rs
index 2f971cabc..093828f17 100644
--- a/crates/voicevox_core/src/infer/runtimes/onnxruntime.rs
+++ b/crates/voicevox_core/src/infer/runtimes/onnxruntime.rs
@@ -296,13 +296,11 @@ pub(crate) mod blocking {
     /// #     .filename(test_util::ONNXRUNTIME_DYLIB_PATH)
     /// #     .exec()?;
     /// #
+    /// use std::ptr;
+    ///
     /// let ort1 = voicevox_core::blocking::Onnxruntime::load_once().exec()?;
     /// let ort2 = another_lib::nonblocking::Onnxruntime::get().expect("`ort1`と同一のはず");
-    /// assert_eq!(ptr_addr(ort1), ptr_addr(ort2));
-    ///
-    /// fn ptr_addr(obj: &impl Sized) -> usize {
-    ///     &raw const *obj as _
-    /// }
+    /// assert!(ptr::addr_eq(ort1, ort2));
     /// # Ok(())
     /// # }
     /// ```
diff --git a/crates/voicevox_core_c_api/src/drop_check.rs b/crates/voicevox_core_c_api/src/drop_check.rs
index 92fdd5ec0..209c85d16 100644
--- a/crates/voicevox_core_c_api/src/drop_check.rs
+++ b/crates/voicevox_core_c_api/src/drop_check.rs
@@ -1,9 +1,13 @@
 use std::{
     collections::BTreeSet,
     ffi::{c_char, CStr, CString},
+    num::NonZero,
+    ptr::NonNull,
     sync::Mutex,
 };
 
+use easy_ext::ext;
+
 /// dropして良い`*mut c_char`を把握し、チェックする。
 ///
 /// `Mutex`による内部可変性を持ち、すべての操作は共有参照から行うことができる。
@@ -26,8 +30,8 @@ pub(crate) static C_STRING_DROP_CHECKER: CStringDropChecker = CStringDropChecker
 pub(crate) struct CStringDropChecker(Mutex<Inner>);
 
 struct Inner {
-    owned_str_addrs: BTreeSet<usize>,
-    static_str_addrs: BTreeSet<usize>,
+    owned_str_addrs: BTreeSet<NonZero<usize>>,
+    static_str_addrs: BTreeSet<NonZero<usize>>,
 }
 
 impl CStringDropChecker {
@@ -46,8 +50,8 @@ impl CStringDropChecker {
             owned_str_addrs, ..
         } = &mut *self.0.lock().unwrap();
 
-        let ptr = s.as_ptr();
-        let duplicated = !owned_str_addrs.insert(ptr as usize);
+        let ptr = s.as_non_null_ptr();
+        let duplicated = !owned_str_addrs.insert(ptr.addr());
         if duplicated {
             panic!(
                 "別の{ptr:p}が管理下にあります。原因としては以前に別の文字列が{ptr:p}として存在\
@@ -69,7 +73,7 @@ impl CStringDropChecker {
             static_str_addrs, ..
         } = &mut *self.0.lock().unwrap();
 
-        static_str_addrs.insert(s.as_ptr() as usize);
+        static_str_addrs.insert(s.as_non_null_ptr().addr());
         s
     }
 
@@ -85,7 +89,7 @@ impl CStringDropChecker {
             ..
         } = &mut *self.0.lock().unwrap();
 
-        let addr = ptr as usize;
+        let addr = NonZero::new(ptr.addr()).expect("ヌルポインタは解放できません");
         if !owned_str_addrs.remove(&addr) {
             if static_str_addrs.contains(&addr) {
                 panic!(
@@ -103,6 +107,13 @@ impl CStringDropChecker {
     }
 }
 
+#[ext]
+impl CStr {
+    fn as_non_null_ptr(&self) -> NonNull<c_char> {
+        NonNull::new(self.as_ptr() as *mut c_char).expect("comes from a `CStr`")
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use std::ffi::{c_char, CStr};
diff --git a/crates/voicevox_core_c_api/src/lib.rs b/crates/voicevox_core_c_api/src/lib.rs
index 38d4706b6..45adec387 100644
--- a/crates/voicevox_core_c_api/src/lib.rs
+++ b/crates/voicevox_core_c_api/src/lib.rs
@@ -1071,7 +1071,7 @@ pub unsafe extern "C" fn voicevox_synthesizer_synthesis(
     style_id: VoicevoxStyleId,
     options: VoicevoxSynthesisOptions,
     output_wav_length: NonNull<usize>,
-    output_wav: NonNull<*mut u8>,
+    output_wav: NonNull<NonNull<u8>>,
 ) -> VoicevoxResultCode {
     init_logger_once();
     into_result_code_with_error((|| {
@@ -1137,7 +1137,7 @@ pub unsafe extern "C" fn voicevox_synthesizer_tts_from_kana(
     style_id: VoicevoxStyleId,
     options: VoicevoxTtsOptions,
     output_wav_length: NonNull<usize>,
-    output_wav: NonNull<*mut u8>,
+    output_wav: NonNull<NonNull<u8>>,
 ) -> VoicevoxResultCode {
     init_logger_once();
     into_result_code_with_error((|| {
@@ -1182,7 +1182,7 @@ pub unsafe extern "C" fn voicevox_synthesizer_tts(
     style_id: VoicevoxStyleId,
     options: VoicevoxTtsOptions,
     output_wav_length: NonNull<usize>,
-    output_wav: NonNull<*mut u8>,
+    output_wav: NonNull<NonNull<u8>>,
 ) -> VoicevoxResultCode {
     init_logger_once();
     into_result_code_with_error((|| {
diff --git a/crates/voicevox_core_c_api/src/object.rs b/crates/voicevox_core_c_api/src/object.rs
index 5cd6aa3df..21dad1159 100644
--- a/crates/voicevox_core_c_api/src/object.rs
+++ b/crates/voicevox_core_c_api/src/object.rs
@@ -64,9 +64,9 @@ pub(crate) trait CApiObject: Default + Debug + 'static {
             let i = Self::heads().push(Default::default());
             NonNull::from(&Self::heads()[i])
         };
-        Self::lock_known_addrs().insert(this.addr_without_provenance());
+        Self::lock_known_addrs().insert(this.addr());
         let body = parking_lot::RwLock::new(body.into()).into();
-        Self::lock_bodies().insert(this.addr_without_provenance(), body);
+        Self::lock_bodies().insert(this.addr(), body);
         this
     }
 }
@@ -86,7 +86,7 @@ impl<T: CApiObject> *const T {
         let this = self.validate();
 
         let body = T::lock_bodies()
-            .get(&this.addr_without_provenance())
+            .get(&this.addr())
             .unwrap_or_else(|| this.panic_for_deleted())
             .read_arc();
 
@@ -103,7 +103,7 @@ impl<T: CApiObject> *const T {
         let this = self.validate();
 
         let body = T::lock_bodies()
-            .remove(&this.addr_without_provenance())
+            .remove(&this.addr())
             .unwrap_or_else(|| this.panic_for_deleted());
 
         drop(
@@ -125,7 +125,7 @@ impl<T: CApiObject> *const T {
 impl<T: CApiObject> *const T {
     fn validate(self) -> NonNull<T> {
         let this = NonNull::new(self as *mut T).expect("the argument must not be null");
-        if !T::lock_known_addrs().contains(&this.addr_without_provenance()) {
+        if !T::lock_known_addrs().contains(&this.addr()) {
             panic!("{self:018p} does not seem to be valid object");
         }
         this
@@ -147,13 +147,6 @@ impl<T: CApiObject> NonNull<T> {
     }
 }
 
-#[ext]
-impl<T> NonNull<T> {
-    fn addr_without_provenance(self) -> NonZero<usize> {
-        NonZero::new(self.as_ptr() as _).expect("this is from `NonNull`")
-    }
-}
-
 #[ext]
 impl<T: CApiObject> T {
     fn lock_known_addrs() -> impl DerefMut<Target = HashSet<NonZero<usize>>> {
diff --git a/crates/voicevox_core_c_api/src/slice_owner.rs b/crates/voicevox_core_c_api/src/slice_owner.rs
index cedcd7417..68d3a50fc 100644
--- a/crates/voicevox_core_c_api/src/slice_owner.rs
+++ b/crates/voicevox_core_c_api/src/slice_owner.rs
@@ -1,4 +1,4 @@
-use std::{cell::UnsafeCell, collections::BTreeMap, ptr::NonNull, sync::Mutex};
+use std::{cell::UnsafeCell, collections::BTreeMap, num::NonZeroUsize, ptr::NonNull, sync::Mutex};
 
 /// Cの世界に貸し出す`[u8]`の所有者(owner)。
 ///
@@ -16,7 +16,7 @@ use std::{cell::UnsafeCell, collections::BTreeMap, ptr::NonNull, sync::Mutex};
 pub(crate) static U8_SLICE_OWNER: SliceOwner<u8> = SliceOwner::new();
 
 pub(crate) struct SliceOwner<T> {
-    slices: Mutex<BTreeMap<usize, UnsafeCell<Box<[T]>>>>,
+    slices: Mutex<BTreeMap<NonZeroUsize, UnsafeCell<Box<[T]>>>>,
 }
 
 impl<T> SliceOwner<T> {
@@ -37,16 +37,16 @@ impl<T> SliceOwner<T> {
     pub(crate) unsafe fn own_and_lend(
         &self,
         slice: impl Into<Box<[T]>>,
-        out_ptr: NonNull<*mut T>,
+        out_ptr: NonNull<NonNull<T>>,
         out_len: NonNull<usize>,
     ) {
         let mut slices = self.slices.lock().unwrap();
 
         let slice = slice.into();
-        let ptr = slice.as_ptr() as *mut T;
+        let ptr = NonNull::new(slice.as_ptr() as *mut T).expect("comes from a slice");
         let len = slice.len();
 
-        let duplicated = slices.insert(ptr as usize, slice.into()).is_some();
+        let duplicated = slices.insert(ptr.addr(), slice.into()).is_some();
         if duplicated {
             panic!(
                 "別の{ptr:p}が管理下にあります。原因としては以前に別の配列が{ptr:p}として存在\
@@ -67,10 +67,12 @@ impl<T> SliceOwner<T> {
     pub(crate) fn drop_for(&self, ptr: *mut T) {
         let mut slices = self.slices.lock().unwrap();
 
-        slices.remove(&(ptr as usize)).expect(
-            "解放しようとしたポインタはvoicevox_coreの管理下にありません。\
-             誤ったポインタであるか、二重解放になっていることが考えられます",
-        );
+        NonNull::new(ptr)
+            .and_then(|ptr| slices.remove(&ptr.addr()))
+            .expect(
+                "解放しようとしたポインタはvoicevox_coreの管理下にありません。\
+                 誤ったポインタであるか、二重解放になっていることが考えられます",
+            );
     }
 }
 
@@ -108,7 +110,7 @@ mod tests {
                 (ptr.assume_init(), len.assume_init())
             };
             assert_eq!(expected_len, len);
-            owner.drop_for(ptr);
+            owner.drop_for(ptr.as_ptr());
         }
 
         fn vec<T: Clone>(initial_cap: usize, elems: &[T]) -> Vec<T> {
diff --git a/rust-toolchain b/rust-toolchain
index 6b4de0a42..bd0f9e6c2 100644
--- a/rust-toolchain
+++ b/rust-toolchain
@@ -1 +1 @@
-1.83.0
+1.84.0