Checkmarks mark your current path. You can click on any point along the checkmarked path to reset from the clicked point. The Final Reward only requires you get all the "End Points," so you can actually skip a few story points that go to the same end point. Here is the bottom part of my first story, with Final Reward completed:
You might be surprised by how closely we (and other regions) work with Nexon Korea, and how many of the changes have come as a result of our collective feedback. While we don't get everything that KMS gets, and we don't always get it right away, it isn't like we have no impact on the game.