Chapter 51

No, Knock it Off, Iida! (だめだやめとけ飯田くん Dameda yame toke Īda-kun) is the fifty-first chapter Kōhei Horikoshi's Boku no Hero Academia.

Summary
Izuku exits the train and starts running towards Hosu to help Gran Torino against the the Noumu-like creature.

Gran Torino had smashed the Noumu-like creature into a small building. The Noumu-like creature slashes at Gran Torino but the elderly Hero jumps out of the way in time, dodging its attack. Gran Torino sees that the Noumu-like creature is about to attack two civilians. Gran Torino jumps at the Noumu-like creature in order to save the civilians. However, the Noumu-like creature is scorched by flames, forcing Gran Torino to stop his attack and back away. Endeavor, the Hero who scorched the creature, says that he hasn't made acquaintances with the elderly Hero, telling Gran Torino that he will deal with the Noumu-like creature.

Izuku has arrived in Hosu and witnesses a battle between the Pro Heroes and two Noumu-like creatures. Izuku is surprised that Tenya isn't at the battle and starts pondering. Izuku quickly figures out that Tenya came to Hosu to find and hunt down the Hero Killer Stain. Izuku leaves the battlefield and searches for Tenya.

On top of a building, Tomura praises the three Noumus for their destruction. Black Mist asks Tomura if he will join the attack, however, Tomura replies that he won't because he is injured. Tomura says that when dawn breaks the world will forget about Stain.

The battle between Tenya and Stain begins; Tenya attacks Stain with a high speed kick, but the Hero Killer dodges Tenya's fast kick with ease by jumping above him. Stain kicks Tenya's right arm, causing it to bleed and slams Tenya onto the ground with his left foot. Stain stabs Tenya's left shoulder with his katana which defeats Tenya. Stain reveals to Tenya that he let Tensei live in order to feed rumors. Stain says that both him and his brother are weak because they are fake Heroes. Tenya, even though he is defeated, rebukes Stain's claim that his older brother Tensei is weak, yelling that Tensei was a splendid Hero and that he will kill Stain to avenge his older brother. Stain tells Tenya to save the injured Pro Hero behind him, surprising Tenya. Stain preaches to Tenya that he must act selflessly by rescuing others first and not be selfish by brandishing his power for his own sake. Stain states that seeking revenge just to satisfy one's selfish desires is the act furthest from the title of "Hero" which is why he will die now. Stain stomps his foot on Tenya's head and prepares to kill Tenya with his katana, saying that Tenya will be an offering to a just world. Tenya refuses to listen to Stain's preaching, yelling that Stain is just criminal scum who hurt his older brother.

Stain is about to deliver the finishing blow. However, Izuku suddenly appears, having activated One For All throughout his body and punches Stain in the face with his enhanced might, preventing the Hero Killer from finishing off Tenya. Izuku announces his arrival and declares that he came to save Tenya.