Saint Ishiyama Academy Arc

The third story arc in the series, the Saint Ishiyama Academy arc is comprised of Chapters 48-76 in the Manga and Episodes 25-36 in the Anime. This arc details on how the delinquents of Ishiyama High are being transferred to their sister school, Saint Ishiyama Academy, as well as the introduction of the Rokkisei. This arc is also the first to give major glimpses of Oga's and Furuichi's past, mainly from when they were in middle school.

Synopsis
Spoiler warning: Plot and/or ending details follow.

Class Arrangement
On September 1, at the start of the new semester, Oga is told by Furuichi that they'll be transferring to Saint Ishiyama Academy while Ishiyama High is currently being reconstructed. They head to the school and enter their classrom, where it's revealed that the other delinquents such as the MK5, Red Tail, and Tōhōshinki are also in the same class, despite their age groups ranging. The students discuss this issue with one another until their teacher, Takumi Sadohara, arrives.

Sadohara starts off by degrading the class, telling them of their delinquent attitudes and their meaningless violence. He then tries to make some examples out of the class by starting with Himekawa, but the third-year retorts by unraveling personal information about Sadohara that he gained from his cell phone. Sadohara is clearly scared about it and decides to gain the class's respect by resorting to their idealistic views, mainly with violence. He challenges Tōjō to an arm wrestling match but easily loses. Finally, he decides to go after Oga and take the delinquent to the principal's office for sleeping. He also accidentally wakes up Be'el and is electrocuted instead. A substitute filled his place for the rest of the day.

Introducing the Rokkisei
One day, a St. Ishiyama student named Kazuya Yamamura is walking to the classroom for the Ishiyama delinquents and notices the Red Tail members standing altogether. Kazuya starts spying on them until Azusa Fujisaki, a childhood friend of Kazuya's, suddenly appears. Startled, Kazuya then leaves with Azusa and tries explaining why he's so interested in delinquents but Azusa already knows. She figured it out throughout the summer when Kazuya dyed his hair and pierced his ears. As they walk, they notice Hajime Kanzaki along with Takeshi Shiroyama and Shintarō Natsume. Azusa notes how scary Kanzaki is and asks why Kazuya even wants to be like him, though Kazuya states that it's Oga that he's after. The two then follow Oga and Furuichi as the two are walking home, only to see them get surrounded by Teimō Tech delinquents. Oga starts beating up the delinquents but they then find Kazuya and Azusa, taking the latter two as hostages. Suddenly, Aoi appears and helps defeat the rest of the delinquents, wanting to help Kazuya and Azusa. Just as she is about to leave, Kazuya then asks Oga if he can be the delinquent's disciple. Oga is confused by this offer but agrees anyway.

At the end of the day, Kazuya visits Oga at his house so that they can go to school together. Kazuya is surprised by the normality of Oga's house but after knocking on the door, to which Hilda opens while feeding Be'el, he becomes shocked. Kazuya quickly introduces himself to Hilda and Oga leaves for school, though he tries ignoring Kazuya. Kazuya persists, however, and Oga becomes even more annoyed when Kazuya starts calling him "bro". Oga tells Kazuya that he isn't his "bro" and that he should leave him alone, but after Kazuya continuously praises and shows his respect for him, Oga decides to keep him as his disciple. At the train station, Furuichi calls Oga an idiot for doing so but after Kazuya starts praising him as well, Furuichi calls Kazuya a great guy to Oga.

On the train, Furuichi then asks why Kazuya even wants to be a delinquent, especially like the ones at Ishiyama. Kazuya states that while there are students at Saint Ishiyama who are really strong and cool, the delinquents at Ishiyama are much cooler. Oga then asks about the stronger students of St. Ishiyama and Kazuya tells him that they are known as the Rokkisei, a group of students who are involved in many sports clubs and are regarded as the most powerful people in the school. Kazuya adds further that the Rokkisei supervise the school. Hearing this, Oga becomes interested in them and, remembering his goal to hand Be'el to someone stronger than him, decides to target the Rokkisei as they're supposed to be strong both physically and mentally.

Meanwhile, two of the Rokkisei members are shown having defeated several other delinquents from Ishiyama. One talks about how disappointed he was in them while another just looks off in the distance, talking to himself that it's been a while since he's seen Oga.

Later, while in their classroom Furuichi notes how there is a large absence of people including the MK5 and Tōjō. Shōji Aizawa states that Tōjō is out working his part-time jobs but that he doesn't know what happened to the MK5, though he did add that he's been hearing a lot of rumors. Nene says that she has also been hearing rumors, saying that it's the Rokkisei. Hajime comments that it's ruining their reputation. The two then start to argue and are even about to fight, but then Aoi enters the room and asks Oga to come with her. They are briefly interrupted by the other delinquents who make comments about Aoi's words, but Aoi ignores them and takes Oga to see Kido, a teacher who talks about student life. Kido tells the two students that they have an authority ranking over the other delinquents (somewhat) before making them class representatives. After which, the two then return to their classroom.

In Azusa's classroom, two female classmates start making negative comments on the Ishiyama delinquents but Azusa disagrees, shocking the other two. When Azusa starts talking about the incident with Teimō Tech, she is warned to look out for herself and also after Oga. Much to their surprise, Oga and Aoi suddenly appear outside their classroom. Oga asks about Kazuya but Azusa tells him that he's not here. Oga is then pulled away by Aoi but he starts talking about the Rokkisei, causing the St. Ishiyama students to start whispering to one another. Oga and Aoi are then confronted by Ichirō Shinjō and Mitsuteru Sakaki while Furuichi is approached by Miki. Furuichi initially didn't recognize Miki, but when he does, becomes cheerful and exclaims how the two haven't seen each other since middle school. The two then talk about Ishiyama's destruction and also about Oga, and before he leaves, Miki mentions that Furuichi shouldn't try and fight the Rokkisei. Furuichi then asks how to identify the Rokkisei, to which Miki states that they have an emblem on their uniform collar and shows one to him. Furuichi then realizes that Miki is a member of the Rokkisei. In the meantime, Ichirō introduces himself (while adding his nickname) while Sakaki remains silent. Aoi quickly identifies them and accuses Ichirō and the other Rokkisei for wanting to attack anyone who gets in their way. She is corrected by Ichirō who says that they're not using violence, but actually punishment. Aoi is then attacked by Sakaki who uses a bamboo sword against her. Aoi then asks for a ruler from Azusa and uses it in the same manner as her wooden sword, managing to cut off half of Sakaki's sword. Ichriō admits that they underestimated the two and Oga, now excited, gets ready to fight. Oga starts off the match with a trivia questions but Ichirō ignores him and punches Oga in the face. Kazuya then appears and scolds Oga for picking a fight with Ichirō, stating that the Rokkisei has won all of his boxing matches with a single knockout blow and is ranked 2nd best in all of Japan. Suddenly, Oga gets up and berates Ichirō for refusing to answer his question. He asks again but is interrupted with another punch, to which Oga then hands Be'el to Aoi so that he can start dodging; it turns out that Oga couldn't dodge the first and second punches because he wanted Be'el to know the answer to the questions he was asking. Ichirō tries to land more punches and kicks at Oga but they're all dodged. Oga asks another question and Ichirō answers it correctly, but then Ichirō loses interest in the fight and leaves with Sakaki.

Aoi and Oga return to their classroom, where they learn about an incident that happened to Shiroyama. While he was trying to defend Yuka and Ryōka from some St. Ishiyama males, he was hit on the head with several dumbbells and sent to the hospital. After hearing this, Kanzaki became enraged and left to attack the ones who beat Shiroyama. Kanzaki eventually finds the students who did it and tries to beat them up, completely ignoring warnings of expulsion. However, he is confronted and then beaten by Miki. Oga, Furuichi, Aoi and Nene arrive afterwards, having originally planned to stop Kanzaki. Nene identifies Miki as a Rokkisei. Miki tries talking to Oga, reminiscing about how close they were in middle school, but Be'el starts yelling angry cries that interrupt Miki. Kazuya arrives and upon being asked, explains more about Miki: he says that Miki is the only first-year student to become a Rokkisei and that he's the captain of the karate club. Soon after, Miki starts mocking the delinquents of Ishiyama High which eventually drives Nene to try and attack him, though Oga manages to stop her. Miki leaves and tells Oga to come to the rooftop, as the other Rokkisei will be there. The delinquents leave but Oga asks Miki who he is, saying he doesn't remember him. Miki is silent.

In their classroom, Himekawa notes how they're being looked down upon. This angers Nene and she asks why he didn't do anything to help, adding further that even if the situation is meaningless to him he should have at least tried to protect his pride. Aoi then says that friends shouldn't fight though Himekawa questions about when they ever became friends. Aoi then notices that Oga is gone, to which Natsume states that he probably went home. He leaves and so does Himekawa, the latter stating that the situation is making him feel unpleasant at the school. Aoi watches as the three leave and tries going after them.

At the rooftop, Oga meets up with four of the six Horsemen: Sakaki, Miki, Ichirō, and Hiromichi Gō. Gō is upset that Oga is the only one who came but soon afterwards, three others appear. These three are Himekawa, Aoi, and Natsume. They all state their reasons for coming and Gō comments that it's now four against four. Meanwhile, Furuichi watches from the building along with newly-arrived Kazuya and Azusa. Kazuya identifies Gō for Furuichi, saying that the Rokkisei is the most violent person in the school and a member of the Amateur Radio Club. The battles between the four Rokkisei and four delinquents begin: Gō vs Natsume, Himekawa and Aoi vs Sakaki and Miki, Oga vs Ichirō. The Red Tail watches as the eight teenagers fight. While the fight between Gō and Natsume does little damage to either, the battle between the Tōhōshinki and the two Rokkisei result in Aoi getting injured and Miki leaving the battle to fight Oga, who nearly defeated Ichirō in their own match. Miki manages to land a heavy punch against Oga. Aoi rushes to Oga's side, worried, and notes how Miki's attack is based on a martial arts that the military uses. Miki scolds her for interfering in his match but Aoi then lets him resume, remembering to put her faith in Oga. Much to her surprise, she then notices Natsume and Himekawa lose their own battles. Oga gets up from the ground and Miki tries to attack him again but is then kicked by Kanzaki. When Kanzaki tries to get Miki to fight him, Oga kicks the former and states that it's not their fight anymore. Oga and Miki then resume their battle until Miki attempts to use a secret technique but before he can use it, he is interrupted by an unknown female student. The girl is Shizuka Nanami, a member of the Rokkisei, who then starts to berate her classmates for involving themselves in the fight, adding further that "he" is very angry. Suddenly, another Horsemen named Kaname Izuma enters the rooftop and claims that he isn't mad. As Miki starts apologizing to Izuma, whom Kazuya mentions is the most powerful and feared of the Rokkisei, Aoi notices how the other male Horsemen are beginning to cower, as well. As she thinks to herself about this, Tōjō appears having been called out of work by Aizawa.