Partitio is an ambitious man, and he wants to learn all he can about the trade of the Merchant. Part of his journey consists of character-specific Side Stories known as The Scent of Commerce. Whenever Partitio comes across one of these quests he'll have to interact with an NPC in need, and helping them with their troubles will unlock something of use to Partitio.
Scent of Commerce quests appear on the main map, along with chapter quests. The level requirements of each Scene of Commerce quest are quite low. That said, two of the three require a fair amount of traveling (and saving) to complete. You'll put more effort into the Scene of Commerce than you might think going in.
Sai Route
Sai is located in Hinoeuma, in the southeast of the western continent. You can reach the town by traveling to the Canalbrine Bridge, then heading south until you hit the Western Conning Creek Coast. Travel west through the Eastern Sai Sands, then to the Southern Sai Sands. Sai is in the north of the Southern Sai Sands. Climb the hill beside the tavern with Partitio in the party to begin the story.
Partitio will recognize the sigil of Masoud, a legendary Merchant. Check his house and Masoud will stroll up. He's the writer of the Mercantile Manuscript, a book Partitio would love to read... only Masoud would prefer the younger Merchant take a hike. Partitio eventually bargains himself into a test, and he needs to bring Masoud the thing he wants most. What is that? Who knows.
The answer is pretty simple. Check the middle of Sai and you'll see a well. There's a woman in a red dress here who is called Masoud's Daughter. Have her follow the party - Partitio can Hire her for 1,000 leaves - and take her to Masoud. This isn't the correct answer, but it puts you on the right path. Try to Hire Masoud for 5,000 leaves and, impressed, he'll hand over the Mercantile Manuscript Archive Key. You can enter the house beside Masoud to find a ton of useful information on places, enemies, and the world in general.
Tropu'hopu Route
Tropu'hopu is the largest settlement on the island of Toto'haha, Ochette's starting location. To reach it you need to sail to Tano'hana's anchorage, then travel east. You'll be in Tropu'hopu before you know it. Put Partitio in the party, then follow the beachfront east until you arrive at the settlement's Shipyard.
When Partitio arrives he'll find an Affluent Man chewing out an Agent over the price of a ship. All Partitio hears is that the apprentice of a legendary shipwright built the boat, and he's interested. Head up onto the dock to find said apprentice, a woman named Terry. She'll claim the ship isn't for sale... though if it was, it would cost 100,000 leaves. A steep price, to be sure, though hardly unattainable as you progress through the game.
Bring Terry 100,000 leaves and Partitio can Purchase the Unfinished Vessel from her during the day. After a lengthy cut scene you'll have a ship of your own, and you can choose its paint color and the symbol on its sail. The ship will be waiting for you whenever you travel to Canalbrine, or one of the game's anchorages. You can then use the ship to sail a new world map, of sorts, where you can fight enemies as you sail, pick up treasure from the water, and discover locations that are otherwise unreachable. Enjoy!
(Don't like the look of your ship? Take Partitio back to Terry during the day. You can Purchase a Ship Alteration Ticket from her for 20,000 leaves. This will allow you to redesign the ship. You can do this as many times as you like, assuming you have the money.)
Winterbloom Route
Winterbloom is a frosty town in the north of the Winterlands. It's located to the east of Cape Cold, where Osvald begins his journey. Make your way to the Eastern Cape Colds, then north, to the Western Winterbloom Snows. Winterbloom is to the east of the latter route.
Check the east side of Winterbloom with Partitio in the party and someone will call for help from a nearby house. Enter and Partitio will discover that an odd device is playing a distress message on repeat. Its owner, Audley, will enter and explain the device to Partitio... and bemoan his inability to sell it. Partitio suggests recording music onto the thing, and agrees to bring back some musicians to record songs.
There are three NPCs specifically named as musicians that you can bring back to Winterbloom:
- Check the chapel in Flamechurch where Temenos begins his first chapter, on the east side of town. There's a Piano-Playing Cleric here during the day whom you can pull back to Winterbloom.
- Look in Canalbrine's Tavern, on the east side of town. A Violinist is standing near the entrance to the tavern during the day. Take her to Winterbloom.
- Enter Crackridge. There's a Guitarist standing right by the entrance during the day. Pull him and his guitar back to Winterbloom.