Mandarake
Not one Mandarake store, but nearly 30 of them, each with a distinct focus, can be found in the Nakano Broadway shopping plaza. Nearly every otaku culture need is catered to here. If you want a Kamen Rider figurine, head to Mandarake Special 3 on the third floor. If you're a fan of tabletop role-playing games like Warhammer, make a beeline for the Kojosen branch on the fourth floor. Or, maybe you've outgrown otaku culture, and want to sell your goods? Try the third floor buy-back stand.