Stefanie Joosten was born in Roermond, Limburg, in the southeastern of the Netherlands. She was a fan of Pokemon  from an early age. She attended the Bisschoppelijk College Broekhin in Roermond, where she followed a bilingual (Dutch and English) course. Claiming to have been obsessed with the otaku culture since she was young, Joosten decided to study Japanese language and culture at Leiden University. In 2009, she went to Kyoto for a year as part of an exchange program. It was after this experience that she decided she would move to Tokyo after earning her degree back in the Netherlands. While in Japan, Stefanie came into contact with several modeling agencies that happened to specifically seek Western models. She started doing modeling jobs in 2011. After doing numerous small acting roles and commercials, she got a call from a mystery agent who was looking for models to help with an undisclosed video game. Joosten, who had been into Japanese games since childhood, became suspicious when she recognized one of the people during the auditions. She later found out this was the famous video game developer Hideo Kojima, giving her an idea of what she had auditioned for. She was chosen as both the visual and voice model for Quiet, a central female character in the Metal Gear game Metal Gear Solid V: The Phantom Pain. Joosten also sung the song "Quiet's Theme" from the game's original soundtrack.