CustomTime for Naninovel in Unity

CustomTime.cs

/// <summary> Custom Unity Time based on <see cref="System.Diagnostics.Stopwatch"/> </summary>
public class CustomTime : ITime
{
   public float TimeScale { get; set; }
   public float Time { get; private set; }
   public float DeltaTime { get; private set; }
   public float UnscaledTime { get; private set; }
   public float UnscaledDeltaTime { get; private set; }
   public int FrameCount { get; private set; }

   private readonly System.Diagnostics.Stopwatch stopwatch;
   private readonly float defaultTimeScale; // default `TimeScale` that set in first instance
   private float lastTimeScale; // last `TimeScale` before changed 
   private long lastElapsedTicks; // last Stopwatch's ticks in Update method

   public CustomTime(float timeScale = 1f)
   {
       stopwatch = new System.Diagnostics.Stopwatch();
       stopwatch.Start();
       lastElapsedTicks = stopwatch.ElapsedTicks;
       TimeScale = timeScale;
       lastTimeScale = timeScale;
       defaultTimeScale = timeScale;
   }

   /// <summary>Calculate `Time` and `DeltaTime` based on current frame.</summary>
   /// <remarks>Important: Call this method in Monobehaviour.Update()</remarks>
   public void Update()
   {
       CalculateDeltaTime();
       FrameCount++;

       void CalculateDeltaTime()
       {
           long currentElapsedTicks = stopwatch.ElapsedTicks;

           UnscaledTime = stopwatch.ElapsedMilliseconds * 0.001f;
           UnscaledDeltaTime = (currentElapsedTicks - lastElapsedTicks) * (1.0f / System.Diagnostics.Stopwatch.Frequency);

           DeltaTime = UnscaledDeltaTime * TimeScale;
           Time += DeltaTime;

           lastElapsedTicks = currentElapsedTicks;
       }
   }

   /// <summary>Freeze the time.</summary>
   /// <remarks>Info: Before changed, the `TimeScale` cached to <see cref="lastTimeScale"/>.</remarks>
   public void Pause()
   {
       lastTimeScale = TimeScale;
       TimeScale = 0;
   }
   /// <summary>Resume the time.</summary>
   /// <remarks>Info: Resume the time based on lastTimeScale.</remarks>
   public void Resume()
   {
       TimeScale = lastTimeScale;
   }
   /// <summary>Set default `TimeScale` that set in first instance.</summary>
   public void SetDefaultSpeed() => TimeScale = defaultTimeScale;

   public void Speed1x() => TimeScale = 1;
   public void Speed2x() => TimeScale = 2;
   public void Speed5x() => TimeScale = 5;
   public void Speed10x() => TimeScale = 10;

}

Initialize.cs

public class Initialize : MonoBehaviour
{
   private ITime time;

   private async UniTask Start()
   {
       time = new CustomTime();
       await RuntimeInitializer.InitializeAsync(time: time);
   }

   private void Update()
   {
       if (this.time is CustomTime time)
           time.Update();
   }
}