Atsumu was a second-year student at Inarizaki High. He was the starting setter for the Boys' Volleyball Team. He was known as Japan's best high school setter and server. He is the twin brother of Osamu Miya. Atsumu appears to be a carefree, confident person who's usually seen with a lazy smile on his face, though he enjoys provoking people and giving offhand compliments. He can be quite condescending, and somewhat selfish at times. Osamu has described him as someone who doesn't listen to others