Blue is a 26-year-old yoga teacher with brown hair, blue eyes, and pale skin. He wears a blue and white sweater, blue boots, black pants, and a blue scarf. He was abused by his brother, Papyrus when he was young. Blue's real name is Sans, but he hates it. He can create portals but uses them sparingly. He enjoys flirting with Dream and sometimes Ink. He calls Dream "angel boy." Blue has a good relationship with Dream and Ink, is neutral on Nightmare and Cross, and has a complex past with Error.