There are 8 of them in total, but how do you get each of them?
You can unlock half of them by doing the story, and the other half require you to do missions.
The ones you unlock via the story are:
- Sakuraba Industries (complete chapter 3)
- Grenada Galactic Group (complete chapter 3)
- Meredith & Co. (complete chapter 4)
- Candid & Credible (complete chapter 5)
There are some that have quest chains associated with them:
Six Stars requires you to complete two affinity missions: "Prospective Partners" and "A Challenger Approaches" (both available via the BLADE barracks), and you have to have completed chapter 11. You'll have to be around level 40-45 to complete this chain.
Orphean Technologies requires you to complete a normal mission "Rock Base Rescue Operation" (talk to Julius near the BLADE tower to get this mission).
Nopon Commerce Guild requires you to complete the "BFFs" affinity mission (which first requires you complete "The Ties That Bind" affinity mission).
Factory 1.21 requires you to complete "Professor B's Return" (which first requires you to complete the "Mystery Man" normal mission, found in the industrial district).