Hajime Iwaizumi

Iwaizumi is a stubborn but reliable teammate, often filling in Oikawa's spot as a morale booster if needed. He acts supportive to all, including Tobio Kageyama, and calls Oikawa out for his childish antics. He often resorts to violence with Oikawa whenever he teases or provokes him, but this does not change the fact that he cares immensely for him; as shown when he makes an effort to stop Oikawa from either working too hard or losing confidence.

Iwaizumi's firm-yet-caring attitude has led some members of the Aoba Johsai team to look up to and respect him. His underclassmen often gravitate towards him, and he is seen giving calm and light-hearted advice to Kindaichi, which can contrast to how he treats Oikawa. He is also very respectful and does not treat his rivals coldly, as Kageyama still treats him respectfully and Iwaizumi has acknowledged his skills.

It is also seen through some extras by Furudate that, while Iwaizumi can be strong and intimidating, he also has quite the goofy side where he loves monsters and gets excited when he finds an "Oikawa" fish in a book to make fun of Oikawa with.

He hates the attention Oikawa gets from girls, and tends to throw volleyballs at him when he’s flirting with them or he sees girls swooning over him. He hates “pretty boys” who steal all the girls.

Iwaizumi is very athletic, Kentarō Kyōtani has challenged and lost to him in every athletic event he could.

Iwaizumi has dark, spiked-up hair, and thin eyebrows. His eyes are olive green. His hair is dark brown. More often than not, he's shown to hold a serious or irked expression.

While playing volleyball, Iwaizumi wears a standard Aoba Johsai uniform with number four on it. He is otherwise shown wearing an Aoba Johsai school uniform consisting of khakis with dark brown details, a lavender-colored button-down shirt, a dark red tie, and a white blazer. Iwaizumi's uniform appears to be missing the cream-colored vest that goes with the rest of the uniform and appears to be slightly disheveled, with his tie loose around his neck and his shirt left untucked.

Iwaizumi is seen wearing an outfit which consists of a pair of jeans with an oversized dark blue denim jacket over a grey hoodie. He’s about 5’11 and very muscular while not being bulky. he’s very strong yet still decently slim, despite having visibly large muscles.

Since childhood, Iwaizumi has been close friends with Oikawa. The two were often shown watching volleyball matches on television and playing volleyball in their free time. When they were a little older, Iwaizumi accompanied Oikawa to a match in Sendai between Argentina and Japan. He witnessed Oikawa meet with Jose Blanco and saw his friend's dedication to become a setter begin at this point.

As they got older, Iwaizumi witnessed Oikawa push himself to become a great volleyball player. However, he soon saw his friend begin to push himself too hard when he found himself to be no match for Ushijima's raw power and brute force or Kageyama's seemingly gifted abilities. One night, Iwaizumi was able to stop Oikawa from striking Kageyama while he was blinded by rage and was able to help his friend see that, while he stood no chance against someone like Ushijima alone, he has a team to rely on that can help him be stronger. From this, Iwaizumi seemed satisfied that Oikawa appeared to be recovering although he occasionally has to keep him in check at times.

Tōru Oikawa: Friends since childhood, Iwaizumi is Oikawa's closest friend. Knowing Oikawa for so long, Iwaizumi knows him so well that he is able to tell the difference when Oikawa is being genuine or not. Although Iwaizumi often calls Oikawa a variety of insulting nicknames and keeps him in line with threats of physical harm, Iwaizumi still has full faith in Oikawa as the team setter and captain. The two often make a powerful duo that put many teams on edge. Though Iwaizumi often lashes out at Oikawa for his stupidity, he genuinely cares about him and his health, as shown by him consistently reminding Oikawa to take breaks and not overdo himself. Any time that Oikawa appears to doubt himself as a setter, Iwaizumi is quick to remind him of how amazing his skills are. Even after high school, Iwaizumi is shown to still enjoy teasing Oikawa as shown when he sent a selfie of himself and Ushijima to Oikawa.
Kentarō Kyōtani: Iwaizumi is the only third-year to be respected by Kyōtani after the second-year repeatedly challenged him to multiple athletic competitions and lost to the ace every single time. Because of this, Iwaizumi is usually the one tasked with keeping Kyōtani in line, either through verbal warnings or physical violence. Despite this, Iwaizumi is shown to support Kyōtani when he makes a good play and when he begins to connect with the rest of the team. He hates Oikawa.
Takahiro Hanamaki: Hanamaki and Iwaizumi seem close and can be seen around each other at times. Hanamaki is usually the one to team up with Iwaizumi when it comes to teasing Oikawa about different things.
Yūtarō Kindaichi: Iwaizumi is shown to be a stable and comforting figure toward the first-year middle blocker. He is able to tell when Kindaichi starts to doubt himself or become overwhelmed with nerves in a tense situation and is able to help keep him calm and clearheaded. Like several others on the team, Iwaizumi is looked at as a 'cool' figure to Kindaichi when he says or does anything.

Favorite Food: Agedashi Tofu (Japanese: 揚あげ出だし豆とう腐ふ, Agedashi Tōfu).
Current Concern: "Just 1cm more... or 7mm, at least..!" (in regards to his height).
Star Sign: Gemini.
He is the oldest third-year and member on the team.
He is very athletic as shown by him beating Kyōtani in several events such as running, batting, and arm-wrestling.[20]
Similarly, Iwaizumi is also shown to be the current arm-wrestling champion of Aoba Johsai.
When combined, Iwaizumi and Oikawa's first names (Hajime and Tōru respectively) form the word meaning "obstinate" or "dauntless" (Japanese: 一いっ徹てつ, ittetsu).
Iwaizumi's birthday, June 10th, is the death date of Alexander the Great, matching with Oikawa's birthday which is the birthdate of Alexander the Great.
Iwaizumi is one of the few characters whose color palette varies in the manga to anime. In the manga, his hair is black and his eyes are dark brown, but in the anime, his hair is dark brown and his eyes are green.
His skills have been commended by Karasuno's players and coaches and his total stats add up to the same total as Ushijima, one of the top 3 aces in Japan.
While Iwaizumi is taller than average, he's the shortest of the Seijoh third-years and appears to find frustration in this. In the Haikyuu Cross Team Match game, Iwaizumi states his goal is to grow to 185 cm so he'll be taller than Oikawa (who responds that he will push on Iwaizumi's pressure points so he can't grow taller than him).
However, in the end, Oikawa is the one who surpasses 185 cm while Iwaizumi never cracks 180 cm.[9]
In the Cross Team Match game, Iwaizumi says he used to capture cicadas during childhood, but he always let them go afterward (when asked, he said cicadas had a short lifespan, so he took pity on them).
There is a running gag that whenever he and Oikawa are in the same camera shot, Oikawa will block Iwaizumi's face somehow, whether it be him holding a peace sign in front of him or standing directly in front of him.