Gmarket, the e-commerce arm of Shinsegae Group, said Sunday that brands participating in its strategic partnership program are seeing strong sales gains, prompting plans to extend the model into high-potential categories. The platform’s Joint Business Partnership, or JBP, program — through which it works with brands on promotional calendars, advertising plans and product strategies — now includes more than 1,300 brands. Among roughly 100 of the largest participants, transaction volumes have aver