Japantown San Francisco is decent. Generally things are a bit overpriced, but the bookstore, Kinokuniya is enjoyable and most things are MSRP there.
A few shops sell prize figures for about $20-$30. I've only seen Kancolle scales at the bookstore that I didn't even register the price of.
Go to Daiso (Japanese dollar fifty store), get some cute crepes, eat some food and don't expect anything too mind blowing.