[samurai007]

Part of the fun of collecting is digging around until you find all the issues, buying some here, some there, etc.

That said, if the manga are new and in print, any store should be able to order it for you, even if it isn't currently in stock.

If the manga is older and out of print, then you need to search used manga shops. Osaka has some great used manga shops (at least, they did when I was there 10 years ago...) There were 2 main ones I went to: The 1st was in the circular building just south of Namba station, behind the Hard Rock cafe and a little bakery. The store was a U-shaped mini-mall of nothing but used manga shops, maybe 8 or 10 different dealers in all, but all sharing 1 large space that they've cordoned off into mini-shops. This is a great place to find complete sets... several of the dealers make a habit of bundling entire sets together and selling them at a discount. There are also many individual used manga to look through, typically 1/2 cover price.

The 2nd store is near Osaka-Umeda station (not Shin-Osaka, which is further north). Getting off the subway, climb to street level and head east about half a block until you see a covered shopping street that heads south. Follow this street about 2-3 blocks south and on the left you'll find a huge used manga shop (and there is another, much smaller used manga shop on the right less than 1/2 a block before it) This large shop has an astounding selection of books, including many rare manga that I found nowhere else in Japan. They have books there that are literally decades old. However, this shop has the habit of shrink-wrapping nearly all their books, which makes it hard to flip through them, and sometimes you just have to take a chance on something. They are also strict about not allowing bags or backpacks into the store (to prevent shoplifting), but they have lockers in the front of the store where you can put your backpack while you shop. Most of their common manga is 1/2 cover price, like the other used manga shops around, but their older, collectible items can be significantly more.

If you are looking for used manga in Osaka, I definitely recommend visiting both stores, if they are still open and still in the same locations. You might ask around and see if other stores have opened as well. There were several other shops that I'd visit on my manga-hunting trips to Osaka, but those 2 stores were always the biggest and best.