Yotsuya is a teenage boy of average height. He has neck-length brown hair with long bangs framing the sides of his face. He also has black eyes. He is usually seen wearing his school's uniform, a dark blue blazer and dark blue necktie with white stripes over a white polo and gray-blue pants.
Yotsuya is a calm and level-headed boy who doesn't talk much. He is annoyed by Miyoshi's obsession with Border.
- His Japanese voice actor, Ryōhei Arai, also voices Fumifumi Saotome.