The aparment has a great location between Shinjuku station and Shinjuku park. It is really spacious and had all amenities we needed - including a fully equipped kitchen and a washing machine. It was the best apartment we had during our Japan trip.
Ko was friendly and responded quickly. It appeared to me that we did not always understand each other correctly and he appears to use automated messages that do not always work seamless.
We can highly recommend this appartment and would be happy to stay here again whenever we visit Tokyo again!