Like all the best sports anime, Haikyuu!! is fuelled by true friendships: not only good sportsmanship and admiration from one team to another but the unbreakable bonds between teammates as well. No one attains victory all alone: players inspire each other, complement each other, and have each other's backs no matter what.
Audiences fall in love with the show for both its thrilling volleyball matches and the sheer amount of heart it shows. Yet the core appeal of the show is the numerous lifelong friendships formed between these characters, bonds that showcase the show's excellent writing and voice acting of its principal cast.
Kei Tsukishima and Shouyou Hinata
Tsukishima and Hinata are as opposite as the moon and sun: Tsukishima is tall, acerbic, and refuses to let himself care about volleyball, while Hinata is short, sincere, and openly lives for his sport. While the two don't get along at first due to their clashing attitudes, the more time they spend together on Karasuno High's team, the closer they become.
After seeing the strength of Hinata and the rest of his teammates, Tsukishima steadily becomes more passionate about what they do, culminating in the episode "The Halo Around the Moon," where Tsukishima fully embraces his love for volleyball in one of Haikyuu!!'s best episodes according to IMDb.
Asahi Azumane and Yuu Nishinoya
After an incident recounted in the episode "A Toss to the Ace," in which Asahi believed he was to blame for his team's losses and Nishinoya vehemently disagreed, Asahi briefly left the volleyball team and Nishinoya refused to play without him there.
After Hinata and Kageyama persuade Asahi to come back, he and Nishinoya return to being an unstoppable ace and libero duo. Despite Asahi's tough appearance, he has a lot of worries and insecurities, which Nishinoya is happy to crush with his usual blunt honesty.
Ryuunosuke Tanaka and Yuu Nishinoya
Though their friendship isn't as brightly highlighted as some of the rest, they are still a constant background presence throughout the show. The pair are a constant source of comic relief, and are always there when their teammates need support.
Tanaka and Nishinoya get along so well because they are so similar: a loud, brash, and passionate pair who give everything they do their all. Their tendency to get easily fired up especially fits with Tanaka's Pisces sign.
Shouyou Hinata and Kenma Kozume
Kenma is a solitary sort, seldom speaking and preferring his video games to other people. A friendship with a social butterfly like Hinata would be very unexpected, but when they meet in the episode "Decision," they bond over how most people would not expect them to play the positions they do.
After the first match between Nekoma and Karasuno, Kenma and Hinata become fast friends. They have complete faith in the strength of each other's teams and root for them to win, and eagerly await chances to play against each other.
Daichi Sawamura, Koushi Sugawara, and Asahi Azumane
A staple of sports anime is the upperclassmen: the older and wiser students whose experience guides the younger players until they can stand on their own. Daichi, Koushi, and Asahi have been through thick and thin together, and their closeness inspires the new arrivals to Karasuno.
The three know each other well enough to play seamlessly on the court, always supporting and complementing one another. In the episode "The Battle of Concepts," when Karasuno wins their match against Shiratorizawa, they all tearfully embrace, overcome with joy at how far they've come.
Kei Tsukishima and Tadashi Yamaguchi
Tsukishima and Yamaguchi have been friends since childhood after Tsukishima defended Yamaguchi from bullies, and nobody understands them better than they understand one another. They are rarely seen apart, and Yamaguchi calls his friend by the affectionate nickname "Tsukki."
Despite Yamaguchi's timid nature, he is not afraid to deliver some brutal truths if Tsukishima needs it, as seen in the episode "Illusionary Hero." When Tsukishima again looks down on their team for trying so hard even though they might still lose, Yamaguchi grabs him by the shirt and yells at him that nothing means more than their pride as players. Tsukishima is so affected by this that he starts questioning his own behavior for the first time.
Tetsurou Kuroo and Kenma Kozume
Like Hinata being overlooked due to his size, Kenma doesn't look like the ideal setter, which often leads people to wonder why he is there at all. Though Kenma never responds himself, Kuroo is always ready to defend his place on the team.
As seen in the episode "The Neko-Karasu Reunion," it was Kuroo who initially got Kenma into volleyball and encouraged him to keep at it, recognizing his strength. They were each other's only friends as children, and though they have both made several new friends as they grew older, their friendship is still the closest.
Koutarou Bokuto and Keiji Akaashi
Living proof that opposites attract, quiet and focused Akaashi and loud and mercurial Bokuto are almost never seen without each other. They are incredibly in tune at all times, able to easily predict each other's actions, and sharply aware of each other's strengths and weaknesses, making them very tough to beat.
The two share some of the most wholesome moments in Haikyuu!!, such as in the episode "Land vs. Air." As they enter for their match with Nekoma, Bokuto throws his jacket in the air behind him, thinking it will make him look cool. Akaashi catches it without missing a beat, either having seen Bokuto do it before and gotten into a routine or just knowing him well enough to guess what he might do.
Tooru Oikawa and Hajime Iwaizumi
One of the best setter and spiker pairs in Haikyuu!!, Oikawa and Iwaizumi are practically inseparable. Though Iwaizumi is often annoyed by Oikawa's immaturity (which isn't by Oikawa often deliberately angering his friend with his antics), the pair have what Oikawa refers to as a "perfect trust."
Oikawa has complete faith in Iwaizumi's abilities as a setter, never doubting that he will hit the ball when Oikawa sets to him, and Iwaizumi is always there to make sure Oikawa's ambitious nature doesn't turn to self-loathing at the idea of not being good enough. Their partnership is one that other teams fear and that the pair themselves can boast about.
Shouyou Hinata and Tobio Kageyama
The duo that drives the entire show, Hinata and Kageyama are the premier pair of friends in Haikyuu!! After losing to Kageyama in a middle school match, Hinata swears revenge, but when he and Kageyama end up on the same high school volleyball team, they must learn to work together instead of competing against each other.
Soon, their unique partnership pays off in their professional and personal lives. Their quick attacks are attuned specifically to their individual skills (Kageyama's toss and Hinata's high jump), and are terrifying to other teams and awe-inspiring to their Karasuno teammates. In addition, they go from being at each other's throats to always jumping to defend each other from mockery and wholeheartedly trusting each other. While they can be antagonistic toward each other, they also are paradoxically devoted to each other like no one else on the show, which is why their friendship is the strongest and most entertaining in Haikyuu!!