Sorry to keep making separate replies, but just a couple more thoughts on what to do after you land. I'm assuming you are going with alone or with someone who also has never been, and I'm assuming you both don't speak Japanese.
1: Download Google Translate and save a couple of pre translated phrases or questions loaded. This will be useful if you don't have an international Data Plan or are too tired from jet lag to think of a way to phrase something while an airport employee tries to help you. One question I would have ready is "where is the SUICA machine?"
2: Get a SUICA Card to compliment the YEN you have with you. SUICA cards are basically NFC prepaid debit cards. They are green and have a picture of a cartoon penguin on it. They are used all over the place, including restaurants, vending machines, and most importantly, the subway system. Considering how often you'll probably jump in and out of the subway system, these will save you a lot of headaches since you can just tap and go through the turnstyles.
3: The subway system in Japan is unbelievably convenient, cheap, and on time. After your first day you'll probably be pretty comfortable with them, but for me, I didn't understand the whole turnstyle system they have. Basically, you tap a turnstyle with your SUICA card to get into a subway station, you jump on a car, and then when you leave you tap your SUICA card on the exit turnstyles, which charges your card. If there are any issues like you missing a turnstyle, or tapping too many times, they have an employee fix it on the spot. Super convenient.
4: Don't get the Kansai pass or any other pass, really. Most rides on a car are around 1 dollar or so, and the passes are waaaay too expensive even if they includes busses, etc. They might be useful if you are traveling between like major Cities, but even then it might be cheaper to just buy a ticket as an international tourist on the bullet train website.
5: 7/11's, Family Marts, and Lawsons are great places to shop for food, cheaply. Grab 2 onigiri for 2 bucks and you'll be good to go for a while. If you show up later at night, some of the food that you can microwave will be heavily discounted, perfect for stowing away in your room provided you have a refrigerator.
have fun, and feel free to ask any questions! It was a really fun trip for a first timer who didn't speak a lick of Japanese!