diff --git a/include/malloc_unmanaged.hpp b/include/malloc_unmanaged.hpp
index 63ad26b..59b8c54 100644
--- a/include/malloc_unmanaged.hpp
+++ b/include/malloc_unmanaged.hpp
@@ -5,8 +5,46 @@
 #ifndef RAIISAFECUDA_MALLOC_UNMANAGED_HPP
 #define RAIISAFECUDA_MALLOC_UNMANAGED_HPP
 
-namespace safe_cuda {
+#include <concepts>
+#include <memory>
+#include <variant>
+#include <cuda_runtime_api.h>
 
+namespace safe_cuda::unmanaged {
+    using deviceMallocDestroyType = decltype(&cudaFree);
+    using hostMallocDestroyType = decltype(&cudaFreeHost);
+
+    template<typename D>
+    concept CudaArrayDestroyer = std::is_same_v<D, deviceMallocDestroyType> || std::is_same_v<D, hostMallocDestroyType>;
+
+    template<typename T, CudaArrayDestroyer D> requires std::integral<T> || std::floating_point<T>
+    using safePtrType = std::unique_ptr<T, D>;
+
+    /**
+     * \brief It allocates unmanaged memory with cuda runtime API.
+     *
+     * It can allocate unmanaged memory on device and on Host for pinned memory.
+     * \tparam T bare and built-in type.
+     * \tparam D destroyer type. It determines if it allocates on device or pinned host.
+     * \param byteDataSize
+     * \return
+     */
+    template<typename T, CudaArrayDestroyer D>
+    std::variant<safePtrType<T, D>, cudaError_t> cuda_malloc(const std::size_t byteDataSize) noexcept {
+        T *ptr_tmp = nullptr;
+        if constexpr (std::is_same_v<D, deviceMallocDestroyType>) {
+            const cudaError_t error = cudaMalloc(&ptr_tmp, byteDataSize);
+            if (error != cudaSuccess) {
+                return error;
+            }
+        } else if constexpr (std::is_same_v<D, hostMallocDestroyType>) {
+            const cudaError_t error = cudaMallocHost(&ptr_tmp, byteDataSize);
+            if (error != cudaSuccess) {
+                return error;
+            }
+        }
+        return safePtrType<T, D>{ ptr_tmp, cudaFree };
+    }
 }
 
 #endif //RAIISAFECUDA_MALLOC_UNMANAGED_HPP