Solid organ transplant(s) and travel to Japan

I am traveling to Izumo on April 27. I am traveling with my brother to see his daughters after a near death experience here in the US. He is immunocompromised due to this. I know that TSA in the US does accommodations for solid organ transplant recipients. Are there any considerations once we pass customs? We have already purchased insurance for the trip, and have submitted Yakkan Shoumei. What else should we consider?