Once you're approved for a Manga title on NetGalley you'll need a way to read it from right-to-left (vs. left-to-right).
For English translations of Japanese manga, you will most likely see that the NetGalley Shelf App is listed as the only reading option. This is because the NetGalley Shelf App has the ability to allow for right-to-left scrolling, which is best enabled for Japanese translated books where the dialogue begins on the right hand side of the page.
Luckily it's easy to enable right-to-left scrolling within your NetGalley Shelf app. After you open the book in the NetGalley Shelf app, click the Gear icon, then turn off "Scroll Mode" and the "Reading direction" option can be changed. Then choose 'right-to-left' and you're all set!