Mandrake (pronunced “Man Do Ra Kay” in Japanese) is a great Otaku shop chain in Japan, like SuperPotato but stocks a larger variety of stuff.
Second-hand magazines, books, videos, figures, toys and of course video games. There’s a great one in Umeda, Osaka but I’ve also been to the Shinsaibashi store, where I took these pictures a couple of years ago.
Prices aren’t too bad and you can usually find some bargains and a few hidden gems, so definitely worth checking out if you’re in one of the main Japanese cities.
Their site has a list of their stores and addresses in English : http://www.mandarake.co.jp/en/shop/ .