Yukio is Rin's younger fraternal twin brother. Yukio is the youngest person to ever pass the Exorcist qualification exam, attaining a Meister in Doctor and Dragoon and later becomes a teacher at True Cross Academy, where he ironically ends up teaching his older brother. Yukio has teal eyes, dark brown hair, and wears glasses for nearsightedness. He has two moles under his left eye and another one under his mouth.