First my two friends and I went to Tokyo Tower, the tallest bright orange structure in the world. (Okay, so I don't know that for certain, but at 333 meters, if there is any bright orange object that beats it heightwise, it's time to run in terror.) It is also noteworthy in that it unashamedly uses a pink phallic mascot. Inside the tower, in addition to the two observation decks--from which they claim you can see Mt. Fuji, though you'd have to come on the handful of days per year that the air is clear enough--are a number of attractions, including a wax museum and an aquarium.
Afterward we went out for an evening of karaoke. In Japan, karaoke is not limited to standing in front of a bunch of strangers at a bar and singing off-key. A group of friends rents out a private room (usually a few dollars per hour) in the karaoke hall, where they can then order food or drinks or just spend the time singing. Most places have songs not only in Japanese, but also a large selection in English and Korean. The karaoke service itself has a lot of entertaining side effects, such as a meter that appears on the screen to "score" your singing or various echo/key changes. Some actually change your voice so it comes out of the speakers on key, or makes you sound like the opposite sex. This particular karaoke place was offering a special "Greek food" menu in honor of the Olympics. (The item we ordered was pizza with feta cheese, which apparently qualifies as Greek food as far as they are concerned.)
The next day we went to an event called Comiket, which is for buying doujinshi (amateur comics and/or fanfiction). That was a mind-boggling experience. There must have been tens of thousands--if not hundreds of thousands--of fans in attendance. After a mere five hours of that, we were all exhausted and wanted nothing more than to collapse.
I returned home safely, quite glad that I had bought my return ticket in advance.