I managed a one month stay in japan for apx 2000 US. Yes I am amazing at low cost travel. of course I know people that live in japan, so I only had to stay for 3 nights in a hotell. I ended up at daynice hotell in tokyo. I am not sure about the hilton for narita airport, but narita itself is a long ways from any thing in tokyo.
As far as anime and games go you could just mention going to 500000 video and game stores in shinjuku. Personal on that budge you are going to learn how to aviod spending $. I would not recomend picking up anything, just memories. . . yea that is perty much all I got, and a 2 sets of chopsticks at a ¥99 store.
Most of the $ I had left over from basic airfare, hotel, and food went into travel. I spent several hundered getting arround japan, and I only took a cab once, as town I was in at the time had not other options to get from the train station to my friends place.
If you want to keep to that budget and be some what realistic, I would simply talk about the places you walked arround at, and what you saw, who you talked to. be sure to talk about the 5 japanese girls you met that were going out to a rave, but ended up back at your hotell room for all 3 days
(Hey if you are making it all up, might as well make it good)