Yosaku runs a charcoal business out of Ilex Forest, selling to trainers passing through the area. He works alongside Sylvester, who's either his employee or son depending on which version you're watching. When Sylvester's Farfetch'd started acting up and wouldn't obey him, Sylvester came asking for help—but Yosaku basically told him to figure it out himself and train the thing properly.
That changed after Ash and his crew stepped in, caught Sylvester's Farfetch'd, and actually helped him get it under control. Grateful for the assist, Yosaku hooked them up with a hefty load of charcoal before they left.
Content compiled by AnimeList.moe from publicly available sources.
