Went to Japan last spring. Here was one day in Tokyo.
Ate breakfast at Tsukiji Market.
Made an offering at Asakusa temple
Finished Time Crisis in Akihabara
Explored Roppongi district
As an anime fan,an efficient way to spend only a day in Tokyo is definitely Akihabara. With the giant electronics shops, the multi floored video arcades and anime/hentai stores, I found this as my geek paradise. 100 Yen (which is around 1 dollar) to play most arcade game and most of the games are set to easy or moderate. Hentai I had never heard of. Store sections the size of basketball courts dedicated to single platforms of video games.
Two other activities you can try to squeeze in
- visit Studio Ghibli's museum. Think about half a day for the trip and to enjoy it
- for you hentai fans, stay in a love hotel. You can find overnight deals which rival or do even better than booking a normal hotel but these places are generally designed for a few hours stay and not booked in advance. I was totally suprised by how clean and well kept they are - very unlike the image we have of any "no-tell motel" here in the US.