During childhood, Osamu is shown to have black hair. Some time after junior high, Osamu dyed his hair grey. Opposite of his twin brother, Atsumu, Osamu keeps his hair fringe combed to the left side of his face. He has grey eyes with hooded eyelids. Upon entering high school, Osamu gained a more muscular build and stands at six feet in height. Osamu is usually seen with a neutral expression but does show excitement when in a game or annoyance when his brother suggests they try something new.