There are a lot of card shops in Japan but they aren't evenly distributed. There are at least 20 in the Kanto region (including at least 12 in Tokyo) but I only know of about 12 that are outside of that area. Osaka, the third most populous city in Japan after Tokyo and Yokohama, has only one shop that I know of - the Mint Umeda store.
Mint Umeda is located in the Hankyu Sanbangai Mall located just north of Umeda Station (and, yes, it's that Hankyu). The store is in the north building of the mall on the B1 floor which is the first floor below ground level.
This is another one of Mint's "mall stores" and as such it strongly resembles their Shinjuku and Sendai stores that I had previously visited although it's a little bigger than each of them. Much of what the store stocks is recent cards - both as unopened boxes and packs and as singles. The display cases on the walls of the store contain the more expensive cards - autograph and memorabilia cards as well as rare parallels. This store also had a bunch of Calbee and Nippon-Ham cards from the 1970's in one of the display cases. This is not a store that I would recommend doing set building at due to their relatively recent inventory and the fact that their singles are priced at 100 yen a card.
I'm pretty sure they take credit cards here.
The store sells a lot of gaming cards including "Magic - The Gathering". It has a bunch of tables set up for people to play on.
Here's a map showing the location of the store. Note that while the location marked is where the store is, it's not on the floor that's displayed on the map. So don't expect to find a Tully's Coffee or a Taco Bell nearby. The store is on the floor BELOW the one shown.