Kinnikuman was the Japanese origin of M.U.S.C.L.E. Things, those mini-wrestler figures that kids in the US loved back in the 80's. While M.U.S.C.L.E. was limited to just an assortment of small PVC figures in the US, Kinnikuman was a fully-realized property in Japan, with a comic and cartoon series accompanying a huge merchandising blitz. It was a pretty big fad over there, and it's still strong enough today that entire stores can be devoted solely to Kinnikuman collectibles.
One such store is the "Muscle Shop" in Osaka! Kinniku-fan Noah reports:
It is an official store that will only be open until 2015. They have a limited supply of classic figures but they also have several cases of amazing not-for-sale vintage pieces and new items (t-shirts and other memorabilia).
Noah included a crapload of great pics, including one of the store front above and a bunch featuring the store interior below. Check out that crazy Kinnikuman statue! Show him how it's done, Noah!
He also included a couple of pics of the subway station.
Back in my old M.U.S.C.L.E.-collecting days, every once in a while I'd hear about a magical store in Tokyo called "Mandarake" that was similarly devoted to Kinnikuman. Noah reports that the store is still up and running, and snapped a shot of the exterior display!
It is still open (was there at early November, 2013), the directions posted on your site are accurate. It is on the 4th floor of the Sun Mall building. I've attached a pic of the store front and the business card for "Mandrake" the larger collection of stores to which it belongs. For interest there is a great toy store on the third floor that has all manor of wrestling / martial arts toys.
For more on the Mandarake store (including directions) check out Nathan's MUSCLE Blog. I wish I could visit these stores, but considering how much money I'd drop there, it's probably best for me to admire them from afar. Thanks, Noah!