He is the twin brother of Atsumu Miya. 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 gray 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. Post-timeskip, Osamu's appearance has changed very little. Osamu appears to be the calmer of the Miya twins with a laid back and deadpan personality. Despite his outward demeanor, Osamu is highly competitive and becomes heated even if it isn't obvious on the surface. However, with enough provocation, he gets angry and physical. In that state, he abandons his filter and begins spinning profanity. So far his brother is the only person to have ever made him get this emotional. Osamu is also shown to have a large passion for food.
Like his brother, he loses self-control when it comes to eating.
He thinks about it often in the middle of a match and would get distracted by the smell of it. He can't seem to pick a favorite food and wouldn't know what to eat as his last meal. Like his brother, he loses self-control when it comes to eating. In his second year, he decided he would quit volleyball in order to pursue a food-related occupation, which is how he eventually came to establish Onigiri Miya. He's shown to have a sense of humor, especially regarding Atsumu, whom Osamu teases whenever he messes up. Osamu lives in Hyogo Prefecture and attends Inarizaki High School with his twin brother. He is currently a second year and is a member of his school's boys' volleyball team. Together with his brother, Osamu has been playing volleyball since his elementary school days. In the fourth grade, the twins attended a volleyball workshop where they met their current teammate, Aran. They thought foreign sounding names were cool and came up with the nicknames Samu and Tsumu for each other. When asked if he wanted to be a setter, Osamu turned it down saying he prefers to spike. Despite that, he was chosen to be the setter for his junior high team until Atsumu overtook him. It is known that he and Atsumu went to nationals in their first year of junior high and played against Yurisei in their third. Osamu made his first appearance with the Inarizaki team on the second day of the Spring High Tournament as they face off against Karasuno. During his serve turn, Osamu waits out the full eight seconds before serving.
His serve ends up perfectly received by Nishinoya and ends in a point for Karasuno. Later, although reluctantly, Osamu performs the God-Like quick with his brother, Atsumu, delivering the ball to his exact spike point. The twins continue to score with their new quick until Tsukishima shuts it down. After Tsukishima rotates to the back, Osamu finds himself in a 1-on-1 with Hinata now commit blocking him. Although Hinata manages to block Osamu once, Osamu quickly gains the upper hand and spikes pass Hinata's block with ease. Later, Osamu is seen half-assing a run-up attempt since he is only acting as a decoy. He got an earful from Atsumu, who accuses him of being afraid of Hinata's blocks. Osamu says he is not afraid of Hinata but is taken aback when Hinata suddenly questions him if he is being serious. In his next quick attack attempt, Osamu is forced to hit a straight when Hinata choked off the path for a cross. His spike is received and eventually results in Karasuno's break when they employed their blend-and-distract tactic. After this play, Osamu mentions that he is suddenly feeling hungry, to Atsumu's confusion. After Karasuno took the first set, Inarizaki turned up the heat and overwhelmingly dominated their opponents. When Atsumu got the first touch of a chance ball, Osamu acts as a backup setter to set a quick to Suna, demonstrating just how the Miya brothers complement each other on the court.
With Inarizaki gaining all the momentum, the twins continue to make bold and aggressive plays.
However, he and his teammates begin to show signs of instability once Karasuno starts exerting pressure. When Atsumu taunts Osamu about beating him in service aces, Osamu becomes agitated enough to lose control in his serve and hit it hugely out of bound. Inarizaki eventually regains their composure and won the second set once their captain Kita is subbed in. In the third set, Osamu continues to show off his all-rounder prowess. He successfully receives a jump floater serve from pinch server Kinoshita, ending Karasuno's serve in one turn. He and Atsumu eventually forced Karasuno into a corner when Osamu pulls off a minus-tempo toss to Atsumu. With Inarizaki gaining all the momentum, the twins continue to make bold and aggressive plays. Almost as a response to his quick being limited and blocked by Tsukishima, Osamu re-sets a toss to Aran after Atsumu sends him a toss on the first touch.
The play successfully fools Karasuno's blockers as Aran blasts a spike to open space. The spike ends up received by Hinata and results in a long hard-fought rally that concluded in a lucky net-in for Inarizaki. Despite widening their lead, Osamu recognizes the change in atmosphere with Karasuno. He has been quietly observing Hinata for a while and finally voices his thoughts to Atsumu. Osamu compares Hinata's passion for the sport to eating a meal as well acknowledging just how infectious such hunger can be to his teammates. True to his observation, Karasuno regains their composure and soon caught up to Inarizaki. With the match counting down to its final points, Osamu is shown to be just as fired up if not more so than Atsumu. Despite being less than enthusiastic about the God-like quick in the beginning, Osamu is now the one initiating the attack and exerting pressure on Atsumu to send the toss to him. Atsumu fully relishes in his brother's greed to score and decides there's no one better to use as decoy much to Osamu's annoyance. When they saw Karasuno's receivers out of formation after returning a nearly impossible ball, the twins take advantage of the momentary confusion to attempt a minus-tempo back attack. The surprise attack takes Karasuno by surprise but is ultimately shut down when Hinata and Kageyama successfully block it, thus giving Karasuno the match point.
39;s stress after getting blocked multiple times despite being the ace and feels bad for him.
Afterward, Osamu realizes that they went too wild with their last play. After their loss, the twins try to apologize for losing the final point before Kita rejects their attempt. We tell them that their last play is not a mistake, but rather it is because of their opponent. When Kita expresses how proud he is of his teammates and his regret for not being able to play with them longer, both Atsumu and Osamu claim they will be teammates. Atsumu is irritated while watching the game since he's annoyed at how Kageyama uses his brain during the game and insults him. Osamu admits that he doesn't know Kageyama as well as his brother but suggests that it's probably not a good idea to go that far. And while Atsumu continues twig, Osamu does not listen and thinks about food. Soon after, Osamu notices Asahi's stress after getting blocked multiple times despite being the ace and feels bad for him. Kageyama sets for Asahi and Osamu praises him for this, which irritates his brother. Despite this, they both break into laughter once Asahi finally surpasses Kamomedai's blockers. Osamu also finds disturbing how quiet Hinata was being, although he was not being quiet at all, but instead putting thoughts in his actions. Soon after, Hirugami fails to block Asahi's spike since it waterfalls, but he manages to digit it. We are impressed by this, which leads to Atsumu telling that he and Osamu played against Yurisei in middle school, but he said that at the time he was still really good but was acting more 'possessed' in a way.
Atsumu bursts into laughter once Hinata is able to jump sideways to be used as a decoy and Osamu notices how pleased his brother sounds. In the Final Arc, Osamu is the owner of a successful onigiri business called Onigiri Miya. He attends the match between the MSBY Black Jackals and Schweiden Adlers and sets up a food vendor booth at the stadium. While selling onigiri, Osamu encounters Yamaguchi. The two recognize each other and share excitement about the upcoming match. Later, he chats with Akaashi and mentions about setting up an onigiri shop in Tokyo. When Atsumu missed his first serve of the game, Osamu bluntly states that Atsumu was trying too hard to look good from the start, earning a harsh glare from his brother on the court. During the match, a flashback shows that Osamu had decided to retire from volleyball after graduating high school in favor of a career in food-service. This caused tension between the twins until Osamu challenged Atsumu to see who lives a happier life until their deathbed. The two seem to have reconciled afterward. Atsumu would visit his brother when he was having trouble perfecting his new serve, and Osamu would comfort him with a tuna and spring onion rice ball made with fresh rice received from Kita's rice farm. During the 2021 Olympics, Osamu and Kita are watching Japan's match against Argentina in Osamu's shop. Serves: Osamu performs jump serves and tends to wait the entire eight seconds after the whistle before serving. The time that he waits will add stress to his opponents and throw off their sense of timing.
At times he does show trouble with handling the power of his serves as he at one point sent the ball directly into the scoreboard across the court. Setting: Despite being a wing spiker, Osamu proves he is just as capable as a setter. He has shown the ability to set for the Twins Quick Attack Minus Tempo - Inverse with his twin Atsumu and even resets a toss directed at him while transitioning from spiking form. Blocking: Being one of the taller players on Inarizaki, Osamu is a key player for joining in blocks. He is able to stop several spikes from Karasuno and even easily beat Hinata in a joust. Spikes: Osamu has powerful spikes and is shown to be able to perform a copy of the Minus-Tempo Quick Attack with his brother, Atsumu. Despite their sibling quarrels, Osamu supports his brother however he can. Even after they graduate from high school and pursue their own careers, Osamu is seen helping Atsumu during difficult moments and treating him to special onigiri.