This game can take you from 3-4 hours to dozens by a single playthrough, but you can just know this: main story can be divided to 5 main arcs:
before Jun got smart -> interact with Jun + Church story -> riots -> Melissa story -> leave the city with Jun (last arc)
You can learn how to do these things, one by one, in the community guide
Once you finished a playthrough, got an endings, you will know how this game works, in basic. And you can do other endings, to explore more stories, all of them are noted in the achievements window on the main menu.
Hope these informations can help you.