"We're so excited to show you what's next." Mystery is portrayed as the most enigmatic member of the Saja Boys. He maintains a reserved persona, often striking bashful poses and remaining silent throughout his appearances as an idol. His concealed eyes make it difficult to read his emotions, leaving his mouth as the primary indicator of his expressions. Despite his withdrawn image, Mystery exhibits moments of unexpected aggression. Notably, he barks incoherently at a fan without provocation during a signing event. Additionally, after Jinu sacrifices himself and their plan starts to fall apart, Mystery is the first member of the Saja Boys to charge at HUNTR/X. Mystery acknowledges Zoey greeting him, and barks at the fans when they talk to her, suggesting a protective instinct. His singing voice actor, Kevin Woo, confirmed that Mystery had a crush on Zoey.