I'm not entirely sure as I haven't read it recently. But generally, it might revolve around the adventures of the keeper in the world of lost cities, perhaps facing new challenges, uncovering secrets, or dealing with some sort of legacy left behind in that magical world.
I'm not positive, but I'd assume the keeper is a main character. There might also be some sort of mentor figure or a sidekick that helps the keeper in their journey related to the lost cities' legacy.
I think Uncharted Story is good. The way it unfolds keeps you hooked, and the settings and action scenes are well-done. But, of course, it's subjective - different people have different standards for what makes a story good.
The number of chapters that Absolute Fairy lost was not mentioned in the search results provided, so I don't know how many chapters Absolute Fairy lost.
First, think about their backstory. For example, if they're an adventurer, what led them to this life? Maybe they grew up in a family of treasure hunters. Second, give them unique skills or flaws. A skill could be expert marksmanship, and a flaw could be a fear of heights. This makes them more human. Finally, tie them into the existing Uncharted world. Maybe they have a past with one of the existing characters.