Counter-point

First off, Kyoto is a wonderful place to visit. Be sure to visit a lot of the historical sites, sample the local food and take the Keihan train line down to Osaka (and check out the towns along the way.) As for Tokyo, just stepping outside your residence will surround you with sights to see. Although you're not allowed to stray I guess, you should still have more than enough excitement to fill three weeks.

For a serious Japanese student, you'll want to pick up an "denshi jisho" or electronic dictionary. It's a little flip-open device that contains a English-Japanese dictionary, Japanese encyclopedia, kanji dictionary, and many other functions. It's invaluable if you're going to continue studying and translating the language. I actually only know seven words of Japanese.

As for games, for simple Japanese check out a line of Playstation titles made by D3. They make the "Simple Series" of games, which are all very generic and focused on one function. For instance, The Chess, The Solitaire, The Racing, or for an RPGamer.com visitor: The Dungeon RPG. Those are the actual names. Since they're so simplistic and specific, you'll have a great stepping stone to understanding and learning the Japanese text. So pick out the game that matches your favorite activity (there's literally hundreds to choose from) and you're set! Here's my favorite:

Ha ha! Just kidding! ... moving on...

Alright, so I'm going to give you some classic Do's and Don't's. It'll be like a brain dump as I dig into my past so get ready. As a bonus, just for you, I'm going to be serious about them so pay attention! This is a lesson you can take to the ginko.

DO act courteuous and bow to those you meet. Females usually place their hands together in front of their midsection while bowing.
DON'T overdo it... most times 45 degrees max is more than enough. It's nice to bow in response to another bow, but don't get caught in an infinite loop with it.

DO try many different restaurants and foods, no matter how many tentacles it might have. Even if you hate it, it still makes for a good story... like that time I tried raw horse, Lois.
DON'T be intimidated by new places to eat and drink. You'll almost always be welcomed heartily. You'll meet new friends in the most random of places.

DO learn how to use chopsticks. Yea, it's tough, but it's an endless source of amusement for your new Japanese friends and it's part of good table manners.
DON'T forget to say "itadakimasu" before a meal and "gochisousama" afterwards. It's not just polite, but let's the cook know their effort is appreciated.

DO go to karaoke bars. It's a great way to bond with people and it's fun as balls. You get a private room usually, so you only have to let loose in front of friends.
DON'T watch, sing! Try the Japanese songs too!

DO try fugu. It's a popular delicacy prized for it's taste.
DON'T try fugu. It's really expensive and filled with deadly poison.

DO go to a yakiniku restaurant. It's a place where you order raw meat/fish and grill it yourself. Another great place to bond with new friends while you cook food together.
DON'T forget to remove your meat from the grill before it's black.

DO travel a lot. Trains are pretty cheap, extremely reliable, and can take you to many historic places in under an hour.
DON'T drive anywhere, ever.

DO get a cell phone. I don't even need to explain why.
DON'T commit until you're sure about your phone plan and what charges you will need to pay. For such a short stay, you'll want something you can cancel easily (although there will certainly be a fee.)

DO go to Akihabara. I assume since you're on RPGamer.com, you'll be swept up in the mecca of electronics, gaming and anime that Akihabara is famous for being.
DON'T spend all your money there! You have to eat!

DO talk to everyone you meet. Say "hi," say "konnichiwa," but just reach out to people.
DON'T be afraid to use Japanese. A lot of people get stage-fright and have to ease into Japanese conversation like a hot bath-- that reminds me!

DO visit hot springs! They are some of the most relaxing places on Earth.
DON'T be ashamed if you have to get naked. Spas and hot springs are a wonderful experience, so try to feel comfortable and relaxed. It is possible to find more private places if need be, but the real old-style, authentic ones are not as concerned with modesty.

OK, so where was I? DON'T be afraid to converse in Japanese. You have precious little time so just jump right in and practice. They are impressed no matter how little you know.

DO take lots and lots of pictures.
DON'T forget your camera!

DO enjoy yourself and have a great time!
DON'T forget to write into Japandemonium and tell us how it went!