Is there a way to work for both Duilio and Kuri at the same time? Or do I need like 4 different save files for each different MSQ character? 'Cause that's absolutely annoying.
You'll need 6. It's designed that way as they're storylines take splits. You don't need 6 to eventually see every npc in the game, but they will have their own scenes and boss fights that won't be in other's. The regular fights will be in all 6 paths.