Overall, when travelling inJapan, you should only have to take the ordinary precautions that one would take before travelling. Your family doctor may want to know where you are going in case of any heath problems that may worsen on the trip. Within 20km of the Fukushima Dai-ichi nuclear site, it is still a very dangerous location and it should be avoided due to radiation. There have been natural disasters such as earthquakes and tsunamis in the area at it is important to be prepared for any dangers. Japan is still a developing country and it is suggested that you keep track of your valuables as well.