U.A. Students vs. Nine is a battle fought between U.A. students Deku, Katsuki, Can't Stop Twinkling, Creati, Uravity, Cellophane, Grape Juice, Tailman, Earphone Jack, Tentacole, and Chargebolt against the villain Nine to protect Katsuma and Mahoro Shimano during the Hero Work Recommendation Project.
Class 1-A students are on Nabu Island as part of a program sponsored by the Hero Public Safety Commission, when Nine and his allies suddenly attacked the island. While his allies confronted the students, Nine hunted down a boy named Katsuma Shimano, as his Quirk Cell Activation is essential to his plans and he had to steal it from him. Izuku managed to rescue Katsuma and his sister Mahoro before Nine could achieve their goal, and confronted the villain to protect the children.
During the fight, Izuku discovered that Nine is not only the owner of several Quirks, but also has the ability to steal them, just like All For One. Thanks to this, Nine overwhelmed Izuku in the fight, and when he was about to disposes of Izuku, Katsuki arrived to defeat the villain and works with Deku to fight. Despite this, Nine used his ability to control lightning and defeated the boys. Before losing consciousness, Izuku realized that Nine suffers from an illness if he abuses the use of his Quirks too much, rendering him unable to fight. Slice arrived to take Nine away and signaled to her fellow villains to retreat, at the same time Izuku and Katsuki were rescued by their classmates
Later on the night, Class 1-A regrouped and sheltered everyone to treat the wounded and feed the hungry. Izuku and Katsuki were both unconscious and the doctors could only use their Quirks to close their wounds, but they cannot treat them any further. Katsuma arrived and helped the clinic by using his Cell Activation to heal both Izuku and Katsuki.
Class 1-A held a meeting to discuss their plan going forward. Momo created a drone to send an SOS out to the mainland but won't arrive for six more hours. They tried to figure out what the villains are after and Katsuma revealed that Nine is trying to steal his Quirk. He offered to surrender to Nine to save everyone, but Izuku appeared and stopped him, telling Katsuma he has an amazing Quirk that he should never give up.
Izuku and Katsuki encouraged everyone to fight the villains and protect everyone on the smaller island. Izuku devised a plan of action for the class: Relocating everyone to a large cave under the ruins of Mount Shiroyama, on one of the smaller islands. This way, the villains only have one route to get to Katsuma and everyone has an escape route if needed. Koji, Rikido, and Toru will protect the civilians in the cave.
The remaining students will engage Nine and his gang using the terrain to their advantage and spit the villains apart so they have to face the students alone. To deal with Nine and his multiple Quirks, Izuku noted that Nine can only use his Quirk for a limited time due to the illness he is suffering, so the plan is to have everyone attack in waves to make sure the villain uses his Quirk all the time until he has reached to his limit and hold out until reinforcements from the mainland arrive. When everything is ready and explained, Class 1-A prepared to implement their plan.
The next morning, after recovering from his illness, Nine was determined to take Katsuma no matter the cost. The villains made their way to Mount Shiroyama after Slice scouted them on the ruins of the ancient castle.
As according to plan, the villains approach exactly down the path that Deku predicted. Shouji is the one in charge of guarding Katsuma and Mahoro while Jirou and Ojiro are nearby as the lookout.
The first line of defense consists of Momo Yaoyorozu and Yuga Aoyama. Momo is very tired after using her Creation quirk the night before by providing utilities for the evacuated islanders, but she is still willing to take on the villains. Next to her is a weapon she has created and she keeps hidden under a large cloak with camouflage patterns.
Seeing Nine and his team approach, she orders Yuga to start charging the energy his Navel Laser. When the villains are already in the agreed position, Yuga attacks using his super move "Can't Stop Twinkling: Supernova" to fire a massive navel laser bombardment at the villains. While Nine blocks the attack with his Air Wall Quirk, Slice and Chimera breaks away from the blast, unaware that they are falling right into their trap.
Then Momo removes the cloak and reveals two large cannons she had created using her last fat reserves, and begins firing at the villains, which cause Slide to fall into an underground cavern where she confronts Fumikage and Mina, and Chimera rushes towards a nearby waterfall where he fights Tenya, Shoto, Tsuyu and Eijiro. Momo and Yuga are completely exhausted, but the first phase is accomplished. With Nine's allies driven to designated points, now only the leader remains.
Sero and Ochaco commence their assault on Nine. Sero uses his super move Tape Shot Trident to throw huge boulders at Nine, while Ochaco uses her Zero Gravity to rain down debris on Nine to force him to use his Quirks as much as possible. Nine continues to advance impassively despite their assault, shooting laser beams to destroy the rocks and attack Sero and Ochaco while using the Air Barrier Quirk to block their attacks. They dodge his laser beams and keep throwing more and more rocks at him until he is forced to use his quirks to deflect their attacks at them.
Ochaco is overusing her quirk, and Sero grabs her before she falls down and uses his tape to swing to higher ground, retreating to a certain position where Minoru awaits them with a trap they had prepared: a large amount of rocks contained by wooden posts. Ochaco pushes her Zero Gravity Quirk to the limit to remove the posts, falling to the ground, exhausted, and having to be moved out the way by Sero of the massive rock slide that she caused.
Nine tries to destroy the rocks with his Bullet Laser Quirk, but it isn't enough and he is forced to protect himself by using the Air Wall Quirk. Minoru uses his super Move Super Grape Rush to make the rocks stick together even harder with the sticky spheres from his head, burying the villain under the piles of rocks. Ochaco, Sero, and Mineta celebrate that they have managed to catch the villain, but their joy is short-lived when Nine uses his Quirks to escape the trap. The shock wave knocks down Ochaco, Sero, and Mineta. In the castle ruins, Mezo and Kyoka warn Izuku that Nine broke free and is only thirty meters from them.
On the battlefield, Nine sets out to dispose of the three students when he is forced to protect himself when a light beam from Yuga's Navel Laser attacks him from behind. An exhausted Momo holds Yuga as he continues to shoot, even though he has already reached the limit with his Quirk. Undeterred, Nine defeats the two of them with a strong gust of wind, refocusing his attention on Ochaco, Sero and Mineta.
Nine prepares to launch a powerful attack on them when Katsuki steps in and attacks him with a powerful explosion. Nine is unscathed from the attack and is surprised to see Katsuki alive, who continues to bombard him from the air with his Quirk. After entrusting Mahoro and Katsuma's safety to Mezo, Izuku also intervenes, and attacks Nine with a St. Louis Smash. The villain blocks the blow with his Air Wall and repels Izuku, but Katsuki grabs him by the hand and with his Explode-A-Pult launches him back to attack Nine again.
Although the villain protects himself again with his Air Wall, Izuku's kick was strong enough to push him back several meters. Nine admits they are not doing it wrong. Izuku and Katsuki continue to attack Nine while dodging his counterattacks. Izuku is momentarily distracted by seeing a column of smoke and dust at the place where Tokoyami and Mina are fighting Slice, which almost cost him to be zapped by one of Nine's Bullet Laser if Katsuki hadn't pushed him in time. Katsuki reprimand him for being distracted before returning to combat.
In the ruins, Kyoka warns that in the place where Tenya and his team are fighting against Chimera, a great destruction is also taking place. Mashirao suggests they must go help their classmates but Mezo reminds him that their mission is to protect Katsuma and Mahoro.
Deku and Katsuki continue to fight Nine, as the villain keeps using his various quirks to hold them off. Izuku shoots him several Delaware Smash Air Force while Katsuki does the same with his AP Shot: Auto-Cannon. Nine protects himself from the attacks with his Air Wall and counterattacks with purple light beams, destroying Bakugou's last Grenade Braces in the process.
Nine prepares to shoot them again, but Hanta intervenes and wraps Nine’s arm with his tape and attacks him, but he is defeated after Nine uses his laser to blast him. Katuski yells for his friend as Sero falls to the ground. Then Ochaco takes advantage of the smoke to sneak attack Nine from behind to make him float with her Quirk, but Nine activates his Hydra quirk to attack Ochaco with its jaws and throws her into the air. Deku quickly rushes and catches Ochaco, holding her in his arms.
As he holds Ochako, she apologizes to Izuku for not being able to help him anymore before passing out. Deku lays her gently on the ground to right after furiously fires back along with Katsuki at the summoned monstrous serpent. The creature splits in two and they attack the students, throwing them against a wall. Nine then approaches wounded Deku and Katsuki, who can barely stay on their feet, and attacks them again with his Hydra quirk.
It looks like Nine is finally going to defeat Izuku and Katsuki again, but then the heads of the giant serpents begin to disintegrate. Nine freezes up in pain as his cells start to degenerate, having reached his limits after overusing his quirks. Izuku and Katsuki seize the opportunity they've been waiting for and attack Nine, but the villain activates his life-support to take a heavy dose of empowering drug and goes beyond his limit, using his Weather Manipulation Quirk to summon a massive lightning strike that seemingly vaporized Izuku and Katsuki.
The situation for Class 1-A is growing desperate. Katsuma and Mahoro cry for Izuku and Katsuki, as Mezo continues to protect the kids even though Nine is advancing towards them still. Kyoka and Mashirao tell Mezo to project and take the kids away as they go forth and fight Nine. They ambush the villain in a bridge, which they destroy by using Kyoka's Heartbeat Distortion and Mashirao’s Tornado Tail Dance. Nine falls into the fissure but he quickly summons his giant serpents to escape, smashing Kyoka and Mashirao in the process.
Mezo is about to reach the escape route with the kids, but Nine catches them up and attacks Mezo using his Bullet Laser Quirk. Mezo holds the kids close to him as he blocks them from Nine's attacks. He takes on all of Nine's attacks and is heavily injured, and he tells the kids to run away. The injured Mashirao and Kyoka catch them up and attack Nine with Shoji tackling with his Dupli-Arms Quirk, but the villain uses his Air Wall Quirk at full potencial to blast all three of them away, defeating them.
Nine is in pain by dealing with the constant attacks from Class 1-A members, but with all the students defeated, his prize is finally now at his fingertips.
Nine advances towards Mahoro and Katsuma, who are so paralyzed with terror that they can't keep running to the escape route. Mahoro then fearfully intercedes Nine to try to protect Katsuma and tearfully yells at him to leave her brother alone. However, Nine holds Mahoro hostage and demands Katsuma to come with him if he values his sister's life.
Mahoro begs her brother to run away, and Nine begins to squeeze her neck to silence her. Seeing his sister in danger, Katsuma runs towards Nine in a vain attempt to save her, while bawling and screaming for Mahoro in fear. Nina tosses Mahoro away and reaches out to steal the Katsuma’s Quirk.
Before he can achieve his goal, Izuku enters the fray and kicks him in the face to save Katsuma while Kazuki catches Mahoro before she falls the ground. After recovering from that unexpected attack, Nine is understandably surprised that they survived his previous attack, and they reveal that they did it by using Denki as a lightning rod to absorb the lightning.
More determined than ever to stop Nine's plans, Izuku and Katsuki are ready to keep on fighting to the last breath. The decisive battle is about to begin.