Author's Note
I've travelled to Japan for over 20 years while working at a tech company. This is the course I wish I could have had while struggling with audio courses that plateaued, textbooks that were hard to get into, unusable dictionaries, and teaching methods that looked more like Japanese schoolwork than a genuine attempt at communication. It wasn't technically possible, but now it is, so you can have it.
There's two things you don't do in Japan: Raise your voice or cause someone to lose face. All the other little things you'll figure out (OK, OK, they're here) but those two are fundamental. Japan is a culture of respect. You respect others and carry your weight, and you'll find that others will go to extraordinary lengths to treat you the same.
A week or two in Japan will drain you. You'll spend your days taking transport, seeing things or working in offices, purchasing food, and walking through cities much more dense than maybe you're used to. It drains Japanese people too and you can see it in their faces as well as all the little refuges that they build everywhere from tiny back alley bars, to parks, to shrines. Remember that you're experiencing being in Japan from the UI side. Local people have to produce it, for you and for each other.
With all that said, Japan is extraordinarily open to you. Go out and explore. Go to small places. Be a visitor, not a tourist. Even a basic honest attempt to communicate or to learn the culture will make the people see you as someone who's willing to understand them rather than asking them always to adapt to you. Enjoy Japan!