Izuku Midoriya accidentally dislodges the soda bottles that kept the Sludge Villain contained from All Might's pockets while they were soaring through the air.
The villain escapes and eventually finds Katsuki Bakugo. He takes an interest in Katsuki's quirk and attempts to take over the young man's body. The Sludge Villain envelops Katsuki's body in sludge and takes control of his quirk. Katsuki tries to free himself using his quirk and the explosions draw the attention of nearby Pro-Heroes.
The explosions create fires around the area, prompting Kamui Woods and Backdraft to commence rescue operations. Death Arms and other Pro-Heroes attempt to fight the Sludge Villain in order to rescue Katsuki, but they can't get a grip on the villains fluid body.
The heroes decide as a group to hold out until a hero will an advantageous quirk arrives. Death Arms worries Katsuki may not make it in time as the villain begins to suffocate him. All Might watches from sidelines in his weak form unable to help..
Izuku walks to the scene and watches in horror as he realizes that the Sludge Villain got free. He quickly notices his childhood friend Katsuki is being held hostage and rushes into the dangerous scene despite Death Arms pleas.
The villain becomes irritated by Izuku's arrival and motions to attack. Izuku counters by throwing his notebook into the criminals eye. This disrupts the villain enough for Katsuki to catch his breath. Izuku rushes to Katsuki's side and tells him that he could not sit idly by while Katsuki was dying.
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 inspired by Izuku's actions because the young, timid, and quirkless boy rushed into a dangerous scene in order to save a life. All Might transforms into his muscular state and blocks the villain's explosive attack with his own body. When the smoke clears, Izuku realizes All Might took the brunt of the attack. All Might tells Izuku that he was wrong to lecture him earlier because he wasn't following his own ideals.
All Might rips Katsuki from the villain's clutches, and in one motion, hits the Sludge Villain with a Detroit Smash powerful enough to blow the villain completely apart. 
The air pressure created from All Might's punch is so great that it changes the weather and begins to rain. The by-standards cheer for All Might after his victory. Shortly after Izuku is scolded by the Pro-Heroes for acting recklessly. Katsuki is praised for his bravery and his powerful quirk.
|Chapters||1 • 2 • 3 • 4|
|Episodes||1 • 2 • 3 • 4|
|Fights and Events||Kamui Woods & Mt. Lady vs. Giant Villain • Sludge Villain Incident (All Might vs. Sludge Villain • All Might vs. Sludge Villain: Rematch) • Entrance Exam|