Yun-su

Yun-su is the owner of Dear Crown, a fashion and Prism Stone store right next to Shou's. He is not liked at all by Shou, not because he is his rival in business, but because he is his rival in love. Yun-su has great respect for Aira, and considers her his muse. The clothes he designs are different from Shou's, according to Aira, because they're not cute, but sexy and chique. His sister is Chae-kyoung, and he receives affections from So-min.

(Source: Wikipedia)