Unlock: Liberate the Harmanse Gas & Repair outpost.
In Thurston Town, Seto hires you to retrieve three of his family heirlooms.
The first, his mother’s necklace, is in the possession of a gambler who’s recently lost $300 to three poker sharks inside the Crazy Cock. Enter the bar and play poker with them until you win back his stash. They favor a higher-stakes game than the poker games everywhere else on the island; the “novice” game has a $500 buy-in (!). In order to win back the gambler’s money, you have to force the other three players to bust out and leave the table, which isn’t as hard as it sounds. Return to the gambler for the Necklace. You also get to keep the money you just won.
The drunken privateer is in an alley just far enough outside Thurston Town that you’ll be able to attack him. Kill him and loot his corpse for the Watch; Seto did say that it was theoretically possible to just grab the Watch off the guy after he passed out, but that’s not a Jason Brody plan. Remember, if homicide isn’t the answer, Jason did not understand the question.
The third privateer is having a meeting in a field nearby, with three buddies and their pet dog. Kill them all and loot the target’s body for the Rosewood Knife.
Return the three items to Seto. In addition to the usual monetary reward, this also unlocks the Handbook entry for the Astrid Incident, which involves four familiar-looking people.