After studying sciences, Guillaume joined l’Atelier Letellier in Paris to pursue fashion design.

He began his career in 2001 at Yves Saint Laurent Couture, where he trained in the exacting standards of the atelier as an assistant. He continued at Hermès Homme and later worked alongside Sébastien Meunier, sharpening his eye for menswear creation and stylistic experimentation. He then joined Maison Martin Margiela, taking on a bridge design and production role within a creative environment renowned for its conceptual approach and technical rigor.

Building on this foundation, Guillaume moved to Hanoi to build the menswear line for Mirror Mirror, establishing the creative and structural pillars of a new brand direction. His path then led him into education, first as a Fashion Design Lecturer at ESMOD Seoul, and later at ESMOD Jakarta, where he continues to share his expertise in design, craftsmanship, and collection development with emerging fashion creators.