Osamu Miya (Japanese:
He has a large build and is very similar in appearance to his brother, which shows that they are most likely identical twins. Osamu's hair is dyed gray and his fringe is flipped to his left side.
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 spewing 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. 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 ended up establishing Onigiri Miya.
He's shown to have a sense of humour, 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 sound names are cool and came up with the nickname '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. According to Aran, Osamu was the more skilled twin with Atsumu constantly challenging him.
Tokyo Nationals Arc
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 reluctant, Osamu performs the God-Like quick with his brother Atsumu delivering the ball to his exact spike point. When Aran comments about the trust between the brothers, Osamu denies it is trust but it isn't needed since he just knows the ball will come to him.
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 commit blocking him. Although Hinata manages to block Osamu once, Osamu quickly gains the upper hand and spikes pass Hinata's block with ease. The two players end up in a jousting battle at the edge of the net with Osamu dominating. 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 no 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. 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. 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. Kita tells 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 Kita will be proud of.
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.
It is said that "even if you take down Atsumu Miya, his twin Osamu will be right there to pick up the slack." 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. He also has a powerful jump serve.
Osamu is almost always seen together with his twin Atsumu. As such, Osamu is familiar with Atsumu's every habit,
including Atsumu's tendency to lie and never return borrowed things. As brothers, they are quick to quarrel and fight, but they get over it just as quickly. Osamu is frequently seen teasing his brother, especially when Atsumu messes up in a match. They are each other's biggest rivals and constantly push each other without even realizing it. Nevertheless, Osamu acknowledges that Atsumu's passion for volleyball burns brighter than his own, and is at peace with himself when only Atsumu got selected for the All-Japan Youth Intensive Training Camp.
Their nicknames for each other, 'Samu and 'Tsumu, came about when they met Aran Ojiro in fourth grade because they wanted to sound foreign.
The two faced off when Hinata is assigned to commit block Osamu against the Twin Quick Attack. Although caught off guard at first, Osamu quickly gains the upper hand in both spiking and jousting at the net. After Hinata adapts and alters his tactics to successfully counter Inarizaki, Osamu mentions that he is feeling kind of hungry. He continues to observe Hinata throughout the match and concludes that Hinata's playstyle is akin to eating rice/meal. Osamu recognizes Hinata's hunger for the sport and is aware of how infectious such hunger is to other players.
Osamu is on good terms with the rest of his teammates, enough that he and Atsumu will play jokes on them. Their usual target is Aran, who is often to play the straight man to the twins' gags. Osamu and the rest are shown to be terrified of Kita's cold logic. However, he has nothing but respect and admiration for Kita deep down.
- "Why is it that whenever we're in a game your mental age regresses by, like, five years?" (To Atsumu, Volume 28 Chapter 251)
- "Faith... It's not like I super have faith in 'Tsumu or anythin' like that. S'not like he listens to what you tell him, He doesn't return what's borrowed to him, he's a habitual liar... So it's not like we need faith between us anything like that... I just know that the ball is coming to me." (Volume 28 Chapter 251)
- "Skillswise I'm just as good as you. But I think that, when all's said and done, you love volleyball just a teensy bit more than me." (To Atsumu, Volume 32 Chapter 279)
- "When you're hungry, and you eat a small mouthful of something...it makes you even hungrier." (To Atsumu, Volume 32 Chapter 282)
- Favorite Food: Food
- Current Concern: Not being in the mood to decide what to eat on the last day of his life.
- It is revealed that Osamu is the younger twin. 
- Osamu wears black gym shoes with purple accents.
- When Atsumu and Osamu were fourth-graders, they found Aran Ojiro cool for his foreign-sounding name.
- The Miya brothers attended the same Inarizaki Group Training Camp as Aran Ojiro.
- Although Coach Ukai listed Osamu's, and by extension Atsumu's, age as 16, the Miya twins should have already been 17 by the Spring Interhigh due to having their birthday in October.
- Yako (野狐; lit. field fox) is a spirit possession of foxes in Japanese folklore. Unlike how most of the other schools were named, Yako Junior High School uses the actual kanji of what it's referencing.
- Osamu (治) - To rule/govern
- Miya (宮) - Shrine