SaveFIle.cs

public IEnumerator Save(string filename, byte[] buffer)
{
#if UNITY_UWP
    var task = Task.Run(async () =>
    {
        StorageFolder folder = await GetStorageFolder();
        var file = await folder.CreateFileAsync(filename, CreationCollisionOption.ReplaceExisting);
        using (var stream = await file.OpenStreamForWriteAsync())
        {
            await stream.WriteAsync(buffer, 0, buffer.Length);
        }
    });
    yield return new WaitWhile(() => task.Wait(1));

    // ファイルリストを更新
    yield return Update();
#else
    yield return new WaitForEndOfFrame();
#endif
}