The movie starts with a flashback to Ren back when he was the head of Makada. He and Kashiwara are fighting a bunch of guys in blue uniforms, but Ren breaks away from the group and fights and eventually beats another guy who appears to be the other group's leader. Just as Ren is walking away, however, the guy lurches forward to hit Ren with a lead pipe, and the audience doesn't see the outcome.
The movie then recaps the drama in the opening sequence before coming to the present. The girls are chatting pleasantly with the boys when Shouhei interrupts to announce that the school is going through another merger. It turns out, to their relief, that it's not a merger, but just that they'll be forced to go to school at the first branch of Cattleya for a month. They're alarmed when, on their first day, Fumie and the girls tell them that they have to follow the rules-- meaning no fighting-- for the whole month. They only get one second chance, or else they'll be expelled and won't be able to return to the second branch Catteleya/Makada. They struggle through their first day, much to the girls' exasperation, but the girls are also facing another issue-- the new student body president, Yuka, who was abroad in England while Fumie was the student body president. Yuka is presented generally as a spoiled brat and control freak, and definitely doesn't want Fumie coming back and taking over her influence at first branch Cattleya.
Meanwhile, while on a potty break in the incredibly long queue for possibly the single boys' bathroom in first branch Cattleya, the boys, who up until now have mysteriously only been Tatsuya, Tetsuya, Maya, Satoshi, and Shouhei, run into Yuuki and Makoto, who look none too pleased to see them. Apparently, Yuuki and Makoto had branched from Tatsuya's group when they felt he was going soft, and, being the mature kids they are, aren't speaking to him or their former friends. This is very upsetting to the boys, but since they're all emotionally handicapped, they ignore the problem and go about their lives.
In other parts of the world, Shouhei starts crushing on Catteleya's school nurse. However, Koba-sensei has already been crushing on said nurse, so a rivalry for the ages in how irrelevant to the plot it is begins. After school, the guys are sketched out by Shouhei enacting some weird porno fantasy playing both himself and the nurse during their walk home, but Tatsuya seems preoccupied and excuses himself, saying he has another obligation.
It turns out to be the anniversary of Ren's death. Tatsuya brings flowers to a specific place at the side of the road where one bouquet is already laying. He prays for his brother for a while, remembering his brother saying he had a dream but not explaining what it was. He's in the process of asking Ren to tell him what his dream was when Tetsuya appears. Tatsuya is surprised Tetsuya remembered the anniversary of his brother's death, but Tetsuya, being horrible at human interaction in general, simply puts his bouquet down and prays, as well. The two boys are leaving together when someone approaches on a motorcycle; it's Kashiwara. Afterwards, the three of them sit by the seaside together and Kashiwara explains about the fight from the first scene against a school called KikuKou. Ren went up against their head, Mashima Kenji, and won, but soon after, was in a horrible motorcycle accident and died. Meanwhile, on some sketchy pier somewhere, the current students at KikuKou are beating some people up and seem out for Makada's blood.
Back at the first branch of Cattleya, it's time for their culture festival! Saya and Sayuri offer to give Yuka and her crew advice on how to run a culture festival, but Yuka tells them she knows better than them, causing Saya and Sayuri to get aggressive. Yuka suggests they try to get the most popularity votes at their class's cosplay cafe and determine the winner that way, and Saya and Sayuri agree. Fumie, for her part, doesn't seem to give a crap, and is more caught up worrying about the fact that she has the opportunity to study abroad but doesn't want to leave her friends despite the fact that it's her dream to go to Harvard. Meanwhile, for the sake of "risk management," Yuka has had all the boys locked up in a courtyard and Yuuki and Makoto are forced to face Tatsuya's crew yet again. When Maya tries to break down the door, Yuuki calls him girly, which causes Maya to snap on him. However, when Maya hits Yuuki, Makoto gets defensive of his bff and hits Maya back, starting a brawl. Tatsuya tries to get them to stop, but gets pulled into the fight, and eventually, they accidentally break down the door in their fighting and are discovered by teachers. Yuuki and Makoto escape, but Tatsuya and the guys are chased by the teachers. However, Shouhei manages to hide them in a costume closet, and with a bunch of disguises at their fingertips, the boys cosplay to attempt to escape without being found out.
However, since the boys are incredibly handicapped, Tetsuya and Tatsuya get spotted and chased again. They attempt to hide in a haunted house, but it's restricted to couples, so they grab Fumie and Saya to go with them. Saya recognizes Tetsuya right away, since Tetsuya is an idiot and his costume doesn't really hide his face at all, but Tatsuya, who's in a giant cat mascot suit, is completely hidden. He's also terrified, and Fumie has to hold his hand to get him through the haunted house. When Fumie later finds out it was Tatsuya, she gets all flustered that she held his hand.
Various mishaps happen, but in the long run, the boys save Yuka from her own poor planning and as a result are found out. They get their one strike, and the girls greet them after they receive their punishment to remind them that they don't have another chance. Later (or possibly before, I seriously can't remember the order) it comes out to Tetsuya that Fumie is thinking about going to America, and he's an asshole and tells her not to go. When she finally decides to go, he's even more assholish and asks her if she wouldn't go if Tatsuya told her not to go. He tries to confess to her but she cuts him off and asks him not to tell anyone. However, Saya overhears and pulls Fumie aside, crying at the thought of her best friend leaving her. Fumie comforts her but asks her not to tell anyone either.
Meanwhile, Yuuki and Makoto get into a fight with the guys from KikuKou and manage to get kidnapped. The KikuKou guys call Tatsuya and tell him to come fight them to save his friends, and all of the guys want to go. However, Tatsuya tells them that Yuuki and Makoto aren't their friends anymore so they have no reason to go. The guys are upset, but in actuality, Tatsuya wants to save his friends from being expelled. Fumie catches him in passing and asks him to talk with her, he says he's busy, so they plan to meet at four. Tatsuya's mind is clearly elsewhere however, and he heads towards where the KikuKou guys have Yuuki and Makoto... only to be stopped by Tetsuya. Tetsuya says there's no way Tatsuya can win alone, and Tatsuya replies that he doesn't want Tetsuya to get expelled too. Tetsuya responds that a Makada without Tatsuya doesn't interest him, and so the two set off together.
The fight with the KikuKou guys goes as expected; Tetsuya and Tatsuya can't take the 15 or 20 guys on their own, but soon, Maya, Shouhei, and Satoshi show up to help. Shouhei even manages to be marginally helpful by untying Yuuki and Makoto, who reestablish their friendship with Tatsuya before helping him out. Tatsuya and Tetsuya fight the first and second in command of KikuKou and win... when the scene between Ren and Kenji begins to play out between the head of KikuKou and Tatsuya. The head of KikuKou is about to hit Tatsuya with a lead pipe when Tetsuya saves him, taking the blow instead. However, once he's down, the guy is about to hit Tatsuya again when someone stops him... and it's Kenji. It turns out the current head of KikuKou is Kenji's younger brother and wanted to get revenge on Ren's brother. But Kenji reveals that despite the fact that, in all outward appearances, he and Ren didn't know one another well and were enemies, actually, they had a secret friendship. The other flowers at Ren's grave were Kenji's.
Kenji helps the KikuKou people get themselves back together, and says Tatsuya reminds him of Ren (which is sad and awkward when you think about it). Tatsuya is glad that they won the fight and saved their friends... but remembers he was supposed to meet Fumie. Meanwhile, Fumie bids her friends a tearful goodbye (Saya told them because she couldn't bear the thought of Fumie leaving all alone) and is sad that she never got to say goodbye to Tatsuya as she drives to the airport. However, magically, Tatsuya et al manage to run down her car, and she and Tatsuya say goodbye as friends. The movie ends with Fumie writing a letter to Tatsuya asking him what his dream is. Tetsuya has a similar letter, and the two spend a moment on the roof together before Yuuki and Makoto show up to alert them of a fight and the two run off into the sunset together.
That might have been somewhat disjointed, but that's the gist! I may update this when I see the movie again on Wednesday, or I may not. Hopefully I'll be able to post later with some of my thoughts, at the very least, but I have to say... I loved this movie and can't wait to see it again!