Yun-su owns and designs for Dear Crown, his fashion and Prism Stone store located next to Shou's shop. His designs champion a sexy, chic aesthetic, directly opposing Shou's cute style and fueling a professional rivalry. This competition extends to vying for the affection of Aira Harune, whom Yun-su reveres as his muse and goddess, later acknowledging romantic feelings for her.

South Korean by origin, Yun-su is the older brother of Puretty member Chae-kyoung. Despite his sister's wealth and connections, their relationship remains supportive. Another Puretty member, So-min, harbors unrequited feelings for him, though Yun-su prioritizes his design career. During a farewell, So-min vows to become worthy of wearing his designs upon his return, prompting Yun-su to credit her for giving him courage.

In the Sky High Symphonia arc, Yun-su plays a critical role, collaborating with rival Shou to redesign the Symphonia Series outfits. This joint effort aids Prizmmy and Puretty in rescuing Aira and others from the Symphonia Company, showcasing his ability to set aside personal rivalries for a greater cause.

Following the central conflict's resolution, Yun-su closes Dear Crown to seek global creative inspiration, relocating to Paris. He entrusts his store to Michelle before departing. During his farewell, he challenges Shou to continue their rivalry internationally, signaling mutual respect. His interactions with So-min highlight personal growth as he acknowledges her positive influence.

A future vision depicts Yun-su continuing to travel worldwide, seeking design inspiration, confirming his lasting commitment to his craft beyond the series' events.