Japan is very seasonal so give though to when you will go. Summer is very hot and humid. Winter is very cold, Autumn and Spring are very nice.
Below is a list of top 5 fundamental Japan travel tips:
Japan has four season, each of the season really vary a lot in term of temperature and rain level. It will impact a lot if you did not pay much attention on this and bluntly plan your trip.
Spring season is from March to May, average temperature is 14.5 degree Celsius, normal rain level. Good to have umbrella bring along your trip. Summer season is from June to August, average temperature is 27.7 degree Celsius, most heavy rain fall during this season, must bring a long umbrella. Autumn season is from September to November, average temperature is 18.8 degree Celsius, not much rain at this season, but the temperature different a lot during day and night, need to prepare a jacket. Winter season is from December to February, average temperature is 7.6 degree Celsius, will have snow fall sometimes in January, so need to prepare winter clothing.
However inside building or public transportation there will be heater, so advice is to wear a long sleeves clothing and pair with winter cloth jacket, so you can remove the jacket and more comfortable at indoor.

Japanese is still the main language that widely use in Japan public, private and government body. A lot of younger generation people do speak English but they are speaking in Japanese mixing English term with very strong Japanese pronunciation flavor, so it is very strange or sounds funny when you first time hearing this. No worries, helpers or workers in tourist spots, hotels and restaurant are all well trained with English speaking skill and fluency. If worst come to worst, you still can use your pen and paper to draw some pictures or direction on map that wish to go.
Japan is using 100 volt, with two straight thin flat pin, it is different from some of the Asia country and different to Europe countries too. Digital appliances should be supporting 100 volt – 240 volt, just to make sure, you need to counter check your digital travel gear. Also you need to equip with universal power plug just in case.
All the while Japan tap water is drinkable, just recent years of heavy pollution, some places tap water is no longer drinkable, so before you drinking any tap water either from hotel or public places, need to make sure is there a any sign saying it is directly drinkable or not.
Kyoto. City with amazing temples and the characteristic Gion district full of tea houses and a place to see the Japanese geisha’s. Many Tea Houses and places to dine. The Gion District is awesome to wander around and perhaps see a Geiko or Maiko or at least a tourist or two dressed as one.
Osaka. You can enjoy some of the best food in Japan and there are also many international foods that you can enjoy as well so you don’t go into system shock. The Aquarium is very cool and Osaka Castle and park is fantastic! Ride the Big Wheels, go shopping, wander wound tenmangu etc.
Nara. Nara is an ancient capital of Japan. Todaiji is a must see and a visit to the deer park where you can walk up to and feed deer by hand is an incredible experience.
Ise. Visit the grand shrine. Walk around Oharaimachi an old town with tons of shops and great food. Catch a bus to Meoto Iwa and Futami Sea Paradise.
Kobe. Sannomiya is a great place to shop. Merikan park is enjoyable and a short walk to Chinatown for some good food. Sorakuen garden is very lovely.
Another recommendation is traveling to Okayama and Kurashiki and then up to Hiroshima and Itsukushima.