On Geary is the Japantown Mall (forgot its name, but it's right next to the Kabuki theater, and that's hard to miss. The mall is right in front of the big spiral tower thingy that is like Japantowns "landmark") but they have like five music stores, the prices aren't great, but some stores have an AMAZING selection.
For J-Pop stuff the best place is Mikado, you can buy Ayupans there, and posters and magazines and all sorts of J-Pop stuff. It's the store with the A BALLADS poster in the front window
