Osamu Miya

Atsumu has light bangs, parted to the right, and dyed blonde. His undercut and eyebrows suggest his natural hair color is black. His eyes are large, partially hooded behind half-closed eyelids. After the timeskip, he cut his hair shorter and swept his bangs back from his face. Wears black athletic shoes with blue accents. Atsumu appears carefree and confident, with a lazy smile on his lips. However, he has a complex and contradictory character. He likes to provoke people and disguise insults against them as compliments. At times he acts arrogant, condescending and selfish. According to Osamu, he doesn't listen to others, doesn't return loans, and often lies. A perfectionist with very high standards for himself and his attackers. If they don't meet his expectations, Atsumu isn't afraid to criticize them, including his twin brother. He's extremely sensitive to noise around him during pitching. If disturbed at this point, he completely transforms and becomes frighteningly angry. He's competitive and hates losing, which can sometimes be detrimental to him. Osamu notes that during a match, Atsumu's mental abilities drop to those of a five-year-old.

Osamu Miya, 17, is a 2nd-grader at Inarizaki High School, a volleyball team outside hitter, and Atsumu Miya's twin brother; 183.8 cm (6'11") tall, 74.5 kg (168.5 lbs), and is born on October 5th; has a large, muscular build; his hair is dyed gray (it was light brown as a child), with his bangs parted to the left side; has gray eyes with drooping eyelids that give his eyes a relaxed, slightly distant expression; his face is neutral or calm in everyday life, but during a game or when irritated (especially by his brother), he becomes tense and his gaze is sharp; he looks very similar to Atsumu (they are likely identical twins), the main visual difference being his hairstyle; wears the Inarizaki volleyball team uniform and black sneakers with purple accents; He has an athletic appearance and demonstrates composure, concentration, and physical strength during his serves and attacks during matches. Osamu appears quieter and more composed than Atsumu, but he is also very competitive. Despite his calm exterior, he can become hot-tempered, even if his facial expression is blank. If provoked sufficiently, he becomes extremely angry and loud, using foul language. The only person who has ever caused him to react so emotionally is Atsumu.

Osamu has a sense of humor, especially when it comes to his brother. He often teases Atsumu when he makes mistakes.