A good rule of thumb in Octopath Traveler 2 is to steal/buy/mug/beat up anyone who has an item in their inventory with a diamond next to its name. That means it is a key item that will be important later. (I’d also say if it has an obnoxiously low steal rate with Throne, that’s also a sign you’ll eventually need it.) In the case of the “Descended from Royalty” Octopath Traveler 2 side story, doing so can save you a lot of time later in the game.
So in Clockbank in the second half of town, on the far east side, you’ll see a woman with a drunk man who insists he is a Royal Descendant. That’s even what his name will be.
Now, you can actually prove this. If you go to the Abandoned Village south of Cape Cold (not far from Flamechurch), there is one person still in town. He’s in a house near the eastern exit. If you go into his inventory, you’ll find the Nyx Royal Family Tree. Get that item.
Once you have it, return to Clockbank. Give it to the Royal Descendant. This will finish the Octopath Traveler 2 “Descended from Royalty” and net you 6,000 leaves and a Resistant Nut (M).
Octopath Traveler 2 is available for the Switch, PS4, PS5, and PC. A demo is available.