Well... no one! ( Really. He wasn't a merchant or anything in that sense. ) My master was Sakamoto Ryoma though and he was in charge of the Kameyama Shachū.

( Either of which may or may not be familiar. Kameyama Shachū was a private merchant fleet which became the Kaientai , a private navy fleet, which eventually gave way to the imperial Japanese navy so... H E H. )

He had a lot of other business too though so he wasn't always trading.