During middle school, Oikawa encountered an unbeatable opponent and a prodigy junior that made him insecure of his own progress. After Iwaizumi knocked some senses into him, Oikawa began to value the strength of a team over fighting alone on the court.
When Oikawa won the best setter award in his final tournament of middle school, Iwaizumi pointed out that Oikawa has a genuine smile for once. Oikawa argued that his smiles are always genuine and expressed his joy for having won such an award.
Iwaizumi describes Oikawa as someone carefree but can still be weighed down at times. Despite possessing natural athletic ability and talent, Oikawa was never able to overcome the wall in his way. Wakatoshi Ushijima, a heavy hitter from Shiratorizawa Middle School, was quickly earning a reputation as one of Miyagi's best and managed to defeat Oikawa's team in straight sets all throughout middle school. To make matters worse, a prodigy first year, Kageyama, joined the volleyball club. Kageyama possessed immense potential and soon became a threat to Oikawa for the setter position.
Oikawa began to push himself harder than ever, at times overworking himself and had to be stop by Iwaizumi. His frustrations started affecting his plays as he miss several combos during a practice game. As a result, he was benched while Kageyama was sent in as his sub. During his serve practice after the match, Kageyama approached him and asked to be taught jump serves. The cumulative stress from losing to Ushijima and being outshone by Kageyama pushed Oikawa to his break point. He instinctively react to strike the younger boy but Iwaizumi stopped him before he can.
After sending Kageyama away, Iwaizumi explained that Oikawa was taken out of the game earlier to allow him to calm down. Oikawa declared that can't afford to relax if he wanted to beat Ushijima and advance to nationals. Angrily, Iwaizumi headbutted Oikawa and yelled at him for thinking that he is fighting alone. Iwaizumi emphasized that it's the stronger team of six that will win. Seemingly enlightened by his friend's words, Oikawa suddenly laughed and claimed he feels invincible.
Afterwards, Oikawa quickly returned to his usual lighthearted demeanor; though he still refused to teach Kageyama how to do jump serves. At their final middle school tournament, Kitagawa Daiichi Junior High was able to take a set from Shiratorizawa. Despite losing in the end, they placed second while Oikawa won the best setter award. Oikawa saw the award as proof of his teammates' strength and declared that they will defeat Shiratorizawa in high school. Oikawa also promised Kageyama that he will defeat him if they were to ever face each other.
In the present, Oikawa is next to serve. Iwaizumi reminds Oikawa that he is facing one of his top rivals and should not hold back. Oikawa lets loose a powerful serve. Nishinoya receives it, but ball goes straight back to Seijoh. Both Kageyama and Tsukishima deduce that a quick over the center is the most probable attack option. However, Kageyama directs Tsukishima to block the right side knowing that Oikawa would definitely rely on Iwaizumi in crucial moments. The two Karasuno first years successfully block Iwaizumi to clinch the winning set point.
While Iwaizumi is frustrated at being blocked, Oikawa recognizes that Kageyama is actually looking at the bigger picture and taking into account the trust between players instead of just calculating probabilities. Oikawa suspects Sugawara as a catalyst for Kageyama's transformation from a tyrant to a real king and grows excited over playing the third set.
- Tōru Oikawa
- Hajime Iwaizumi
- Tobio Kageyama
- Wakatoshi Ushijima (flashback only)
- Keishin Ukai
- Ittetsu Takeda
- Makoto Shimada
- Yūsuke Takinoue
- Kei Tsukishima
- Yū Nishinoya
- Daichi Sawamura
- Yūtarō Kindaichi
- Shinji Watari
- Ryūnosuke Tanaka
- Issei Matsukawa
- Nobuteru Irihata
- Sadayuki Mizoguchi
- Shōyō Hinata
- Tadashi Yamaguchi
- Kōshi Sugawara
- Takahiro Hanamaki
- Asahi Azumane
- Akira Kunimi
- Oikawa won his first volleyball award in the final tournament of his third year in high school.
- Kageyama has been playing volleyball as early as his second year of elementary school.
- Kageyama is said to be capable of playing many positions.
- Kitagawa Daiichi Junior High won a set for the first time against Shiratorizawa in the final tournament of the third years.
- To celebrate the successful release of the sixth volume, a center color page of Oikawa with a tissue in his nose and Iwaizumi with a bandage on his forehead. The text reads: “Whether between enemies or allies, there’s an equal amount of drama.”