Mandarake
Not one Mandarake store, but nearly 30 of them, each with a distinct specialty, are found in the Nakano Broadway mall. Every otaku culture need is catered to here. If you want a Kamen Rider figurine, head to Mandarake Special 3 on the third floor, while fans of tabletop role-playing games like Warhammer should make a beeline for the Kojosen branch on the fourth floor. The list of geeky specialties goes on and on.