There's an actual ESP shop that specializes in ESP (but there are other brands too) in Shibuya, not very far from Tower Records.
Although it's where there are the most guitar shops in one place, Ochanomizu is not the only place to find guitars in Tokyo. There are a handful of guitar shops in Shinjuku, Akihabara, and out in the 'burbs. Ibanez are pretty easy to find just about everywhere. At Rock Inn in Shinjuku you can find a VWH often marked down to a nice price. I must be the only person not enamored with this one though. Ha!