Always have a thin jacket with you. My cousin said that the buildings are kept very air conditioned, so it'd feel cold considering how hot and humid it is outside. It's mainly the humidity and be aware of sudden rain.
Are you coming for vacation? Where are you going? What are you interested in doing while here? Some basics would be: All the train ticket machines have an English option. Don't worry about tattoos unless you want to go to a sento/onsen/pool. Hyperdia.com is awesome for figuring out how to get places and what time/track your train is. If your cellphone doesn't get service here, you can rent a phone. Keep a hand towel with you, most public bathrooms don't have paper towel or hand dryers. Speaking of public bathrooms: go into the ones with the pictures of the regular looking toilets.
While I was there I had a blast and I know you will too! Remember to bring a cloth because you will get sweaty in summer due to the humidity. Japan is notoriously safe so people leave their bikes out without locks so you should be fine there When you find the fancy toilets don't be afraid the nozzles are there to clean your butt but it does feel weird at first especially when you aren't expecting it XD Oh when you go to a festival there is a lot of fun things to do and they put on great firework shows (they didn't even stop for a thunder and lighting storm and it was epic) Also don't be afraid to try new food my favorite food now is Takoyaki (octopus balls) but they are so hard to find in the US T.T . Well anyway you should have a lot of fun!
Ooh~ Japan is so fun! I would recommend carrying tissues with you at all times because they might not provide toilet paper in the public restroom, and even hand sanitizer if there isn't any soap. I would also recommend budgeting for souvenirs and be on the lookout for cheap and easy to carry back souvenirs for friends like mini lucky cats~ I don't know how long you'll be there, but food and such can get expensive, so don't feel like you need to go to fancy places all the time, and definitely go at least once or twice to a convenience store~ they have tons of interesting snacks and variations on snacks and candies normally found in the West, as well as really delicious mini meals like onigiri (rice balls filled with meat/fish/other things) ^.^ Have a great time and try as many new things as you can!!
Japan is very etiquette driven so always use good manners. Other than that, I'd agree with what's been said so far. Happy days
Man, I've always wanted to try takoyaki. I bet it'd be so delightfully crispy on the outside and satisfying on the inside.
