The merchant in Wandering Ronin is a special combat class. It has abilities unique to the rest of the classes, in line with the role-playing aspect of the class. The merchant is a combat class, however, and should be treated as such when in battle.
From the Rulebook:
The traveling merchant is a seller and purveyor of goods and services.
They wander from market to market,
buying here, selling there, always looking for profit and advancement.
They are a good source for campaign items as well as gossip and information
about anyone they have sold to.
Examples: Street vendors, traveling convention sales booths, ice cream man.