Toshinori Yagi vs. Sludge Villain: Rematch

Toshinori Yagi vs. Sludge Villain: Rematch is the battle in which seveal heroes face the unnamed Sludge Villain and in which Izuku Midoriya intervenes unexpectedly.

Prologue
After All Might saved his life and trapped the Sludge Villain in two soda bottles, Izuku wants to ask the hero an important question, grabbing onto the hero's leg just as he takes off through the air. This, coupled with the fact that he was running out of his time limit to use the One For All, forced All Might to land on a rooftop.

After recovering from that exciting experience, Izuku asks All Might if a quirkless boy like him could possibly become a hero, only to be shocked to see that his hero had turned into a skinny, sickly looking person. After resigning himself to Izuku finding out the truth about him, All Might decides to explain the situation to him.

Several years ago he received a fatal stomach wound when he was fighting a dangerous villain, and because of that, he can only use his powers for a few hours each day. Using this injury to demonstrate his point, All Might honestly answers to Izuku that someone without a quirk can’t become a hero because they are always risking their life, and because of that he should give up on his dream. Izuku is saddened to hear his hero's response, but he can't do anything but accept the truth, no matter how hard it is.

All Might goes down the stairs to take the villain to the police, but realizes that he does not have the bottles with him. Suddenly, explosions ring out in the city. In turns out Izuku Midoriya accidentally dislodged the soda bottles that kept the Sludge Villain contained from All Might's pockets while they were soaring through the air.

The villain escaped from his confinement, eventually finding Katsuki Bakugo, and decided to take over his body. Sludge Villain envelops Katsuki's body in his sludge and rejoices when he notices knowing that his prey has a powerful Quirk, so he is sure that if he takes control he will be strong enough to stand up against All Might.

Katsuki tries to free himself by using his Explosion Quirk, and the blasts causes great damage in the street, setting fires in several buildings around. This destruction draws the attention of nearby Pro-Heroes, as well as citizens eager to see the heroes in action.

Battle
The explosions create fires around the area, prompting heroes like Kamui Woods, Backdraft, Death Arms and many more to commence rescue operations. Death Arms calls the villain a coward when he sees that he has a student hostage, and attempt to punch him to rescue Katsuki, but he cannot get a grip on the villain's fluid body. The Sludge Villain strike him with his liquid arm. Two heroes approach to try to help, but quickly jump back when the villain attacks them.

Katsuki tries to break free again, releasing more explosions, but the villain is determined not to let his jackpot slip away. Some spectators announce the arrival of Mt. Lady, however she cannot get any closer because she has no room to move in the narrow alley in her giant form. Kamui Woods cannot do anything other than saving nearby civilians, since his Arbor Quirk makes him very vulnerable to the flames generated by Katsuki's explosions. For his part, Backdraft is too busy trying to contain the fires with his Water Pump Quirk, not being able to help until the firefighters arrive.

Death Arms is frustrated that the combination of the villain's fluid body and Katsuki's Quirk gives them no options, and when they try to get close again, the villain attacks them with his liquid limbs. The heroes have no other option to hold out until a hero with an advantageous Quirk arrives, holding back the damage until then. Death Arms worries Katsuki may not make it in time as the villain begins to suffocate him.

All Might arrives to the scene, but can't do anything but watch the battle from the sidelines in his weak form, unable to help. Izuku, who is walking dejected down the street, coincidentally bumps into the incident. Although he considers it not worth it, he decides to watch the battle, only to be surprised that it is the villain who had attacked him before who is responsible for it. Izuku realizes it was his fault that All Might lost the bottles the Sludge Villain was trapped in.

Izuku feels worse about himself when he hears two citizens saying that the villain is holding a junior high schooler hostage, reminding him that he was about to die when the villain did the same to him. Mentally, Izuku apologizes to the unknown student for being in that situation because of him, and asks him to hang on until someone arrives to save him. Meanwhile, All Might doesn’t stop self-deprecating, considering himself pathetic for being unable to do anything.

The Sludge Villain's victim continues to struggle, his eyes visible for a brief moment, and to his horror Izuku recognizes those eyes as Katsuki Bakugo's. Before he even realizes it, without even knowing why and unable to stop himself, Izuku runs towards the villain to save his friend.

His decision takes all the heroes, including All Might, by surprise. Death Arms pleas Izuku to stop, but he continues running. The villain becomes irritated by Izuku's arrival and motions to attack. Remembering the entries he wrote in his hero notebook, Izuku counters by throwing his schoolbag at him, hitting the criminal's eye. This disrupts the villain enough for Katsuki to catch his breath.

Izuku rushes to Katsuki's side and begins claws the villain’s body in a desperate bid to free him. Katsuki asks why he's there, and Izuku replies that he doesn't know, that his legs started to move on their own, but he looked like he was pleading for help. The Sludge Villain recovers and prepares to kill Izuku. The heroes rush to save the young man and a large explosion ensues.

All Might is shocked by Izuku's actions because the young, timid, and Quirkless boy rushed into a dangerous scene to save a life. He chastised himself for his previous weakness of character as he assumes his heroic form once more and joins the fray. He chastised himself for his previous weakness of character as transforms into his muscular state, going beyond his own limit, and blocks the villain's explosive attack with his body.

When the smoke clears, Izuku realizes All Might took the brunt of the attack. The number 1 hero tells Izuku that he was wrong to lecture him earlier because he was not following his own ideals. All Might grab both boys with one hand while the Sludge Villain prepares to attack him. Even as he coughs blood, All Might punches the Sludge Villain with a Detroit Smash to blow the villain completely apart, saving Izuku and Katsuki in the process.

His punch is so powerful that the heroes must protect the bystanders from the air pressure that even changes the weather, causing it to rain within seconds. The bystanders begins to cheer All Might for his victory.

Aftermath
After All Might's victory, the heroes collect the scattered body of the Sludge Villain, putting them in garbage bags, and safely deliver it to the police.

Then, while All Might is interviewed for his prowess, Izuku is harshly chewed out by some of the Heroes for running in so recklessly, and Bakugo are praised by other for their bravery and powerful quirk, even to the point of asking him to join their agency as soon as he can, but it falls completely on deaf ears as Katsuki only frowns at Izuku in silence.

Afterward, as Izuku walks home afterwards, still heartbroken over his dream ending, Katsuki confronts him. With his pride wounded because that someone without Quirk tried to save him, he states that he never asked for help and warns Izuku not to look down on him.

Once Katsuki leaves, All Might appears in front of Izuku, to his surprise. All Might apologizes for what he said to him on the rooftop, and explains that his actions not only inspired All Might to act, but it leads to All Might telling Izuku that he can become a hero, choosing Izuku as his successor and the new heir of One For All.

Upon hearing his words Izuku can't help crying with happiness.