Two years ago, Muscular killed the Pro Hero team known as Water Hose when they tried to protect citizens from him. Muscular lost his left eye as a result of their battle. The members of Water Hose were Kota Izumi's parents.
Everyone would tell Kota that his parent's sacrifice was noble, but Kota believed they chose their heroic duty over raising their son. Their deaths distorted Kota's views on hero society so much that he became cynical and jaded towards heroes and Quirks.
During the Quirk Training Camp, Izuku Midoriya met Kota and tried to help him by talking to him alone. This only served to anger Kota, who isolated himself on a cliffside that he called his secret hideout. When the Vanguard Action Squad invades the Beast's Forest, Muscular finds Kota alone as the young man overlooks the burning forest. 
Izuku goes looking for Kota alone because he knows where Kota hangs out and Mandalay doesn't. Mandalay sends out a telepathic message to Kota, but it's too late as Muscular begins to confront him. The masked villain asks Kota to trade his hat for the mask. Kota runs away and Muscular cuts him off by activating his Quirk and jumping in front of him.
As Muscular begins to attack, his face is revealed and Kota recognizes him as the man who murdered his parents. Muscular tries to crush Kota and Izuku swoops in to rescue the young boy just in time. Muscular mentions that he recognizes Izuku from Tomura Shigaraki's kill list. Izuku begins to worry because he didn't expect to run into any villains and he broke his phone on accident after he grabbed Kota. He also didn't tell anyone where he was going when he left the group, meaning he can't hope for backup.
Izuku stops worrying when he realizes he doesn't have a choice but to fight Muscular on his own. He stands up in front of Kota and tells the young man he will save his life no matter what.  Muscular is both annoyed and amused that Izuku believes he can protect Kota alone. He says that wannabe heroes like to mouth off about justice and then refers to Izuku by name. Muscular reveals that the villains were told to take initiative and kill Izuku on sight. 
Muscular says he's going to torment Izuku and throws off his robe before attacking. Izuku tries to block the villain's quick attack, but his guard is broken and Muscular punches him into the rock wall beside them. The villain takes a moment to ask if Izuku knows where Katsuki Bakugo is, forcing Izuku to realize Katsuki is the target of the villains.
Muscular swiftly dashes at Izuku and punches him with his Quirk enhanced fist. Izuku manages to dodge and clasps his broken left arm. Muscular believes Izuku's silence means he doesn't know and then he kicks Izuku back into the rock wall. Izuku falls and cuts his head open, causing blood to drip down his face. The blood excites Muscular and he mocks Izuku's claim that he would protect Kota.
Izuku mulls over Muscular's Muscle Augmentation Quirk and realizes that he can't worry about Katsuki at the moment. He gets up and reactivates One For All: Full Cowl before trying to hit the villain with an enhanced punch. Muscular easily defends by absorbing the impact with his expanded muscles. He admits Izuku is quick but says that the young man isn't strong enough to deal any real damage. Muscular smacks Izuku away and brags about how his Quirk increases his speed and strength so much that his muscle fibers pop out of his skin.
Muscular claims Izuku's Quirk is an inferior version of his own and tries to crush him with a powerful punch. Izuku dodges in time but the debris created by his opponents punch knocks him in the head. Muscular chases him in mid-air and then punches Izuku back down to the ground while mocking his efforts to become a hero. As Izuku lies down injured, Muscular taunts him by saying he shouldn't make promises he can't keep.
Kota throws a rock at the back of Muscular's head and asks him if he remembers killing the Water Hose heroes. Muscular is surprised to learn that Kota is the child of the heroes who took his left eye. Kota yells at Muscular and tells him that the world is messed up because of crazy people like him. Muscular refuses to take the blame and says their death is a result of everyone involved doing their best in their roles.
Izuku tries to sneak attack Muscular before he attacks Kota. The villain catches on but Izuku is able to lodge his hand between the exposed muscle fibers on the former's arm. This makes it so Muscular can't evade the incoming attack. Muscular believes that Izuku's next move won't matter anyway and starts to attack. Izuku proudly states that it doesn't matter whether or not he can do it, it's simply a hero's duty to risk their lives in order to transform promises into reality. Impassioned, Izuku charges One For All to 100%.
Muscular realizes there is something different about Izuku just as his opponent lands a full powered smash that destroys part of the cliffside. The impact almost knocks Kota over the edge, but Izuku catches him with his teeth and pulls the child to safety. They're both shocked when Muscular reveals himself, having survived the impact by covering himself with muscle fibers. Muscular commends Izuku's attack before stating that it was too obvious.
Izuku tries to buy time by asking Muscular's motives, but the villain only replies that he wanted to be let loose. Muscular goes on to admit that Izuku's actually very strong and replaces his prosthetic eye with his "serious" eye. Izuku tells Kota to hang on to him and quickly moves out of the way as Muscular attacks at full strength. Muscular's punch crushes a large portion of the cliff and Izuku realizes that Muscular was just toying with him before now. The villain unleashes a quick follow up attack and misses. The shockwave created from his punch hitting the rock wall knocks both his targets back down to the ground.
Muscular's arm gets caught in the rock wall and he laments about getting too excited. Izuku strategizes to bring Muscular back to base camp to Shota Aizawa can erase his Quirk. This plan quickly falls apart when Izuku realizes he's too tired from training to outpace Muscular. He decides to stand his ground to give Kota an opening to run. Izuku uses 100% again and counters Muscular's next attack with a Detroit Smash.
Muscular covers his body in muscle fibers and overpowers Izuku. Izuku tells Kota to run while he's holding the villain back. His smash attack is weaker than the previous one and Izuku isn't able to hold back Muscular for long. The villain smashes Izuku into the ground and begins to crush against the ground. Izuku's spirit begins to fade and he silently apologizes to both his mother and All Might.
Before Izuku is crushed completely, Kota uses his Water Quirk to splash Muscular. Kota demands Muscular release Izuku and this distraction is enough for Izuku to regain his fighting spirit. Izuku's power rises and he lifts Muscular from on top of him.
Impassioned once again, Izuku uses One For All at 1,000,000%. He uses Delaware Smash to break apart Muscular's muscle fibers and then punches him with a full power Detroit Smash to break his defense completely. Izuku punches Muscular in the face with the 1,000,000% Delaware Detroit Smash and sends him flying deep into the rock wall, finally defeating the villain. 
Izuku's sacrifice makes Kota recall Mandalay telling him one day that he would meet someone that would make him understand why his parents were heroes. He begins to cry and question why Izuku would risk his life for someone he barely knows. Izuku lives up to Mandalay's words, as he becomes the person who Kota could finally call "My Hero". Izuku stands up and shouts triumphantly to the sky after his victory.
Afterward, Muscular lies defeated in the collapsed rock wall and Izuku nearly collapses himself. Concerned, Kota runs over to him. Izuku says everything is okay and he needs a moment before moving on to his next task. Kota replies Izuku is too injured to do anything else. Izuku clarifies that he needs to warn his teacher and all the students about the powerful villains and their motives to capture the students.
Izuku decides to leave Muscular behind and tells Kota that his water Quirk could put out the fires in the forest. Kota gets on Izuku's back and Izuku uses his Quirk to travel back into the forest. 
- Izuku and Muscular's battle is foreshadowed in Season 3's opening ODD FUTURE. The anime's opening features a short scene of Izuku confronting Muscular, signaling their battle to come during Season 3.
- ↑ My Hero Academia Manga and Anime: Chapter 71 and Episode 40.
- ↑ My Hero Academia Manga and Anime: Chapter 72 and Episode 41.
- ↑ My Hero Academia Manga and Anime: Chapter 73 and Episode 41.
- ↑ My Hero Academia Manga and Anime: Chapter 74 and Episode 42.
- ↑ 5.0 5.1 My Hero Academia Manga and Anime: Chapter 75 and Episode 42.
- ↑ 6.0 6.1 My Hero Academia Manga and Anime: Chapter 76 and Episode 42.
- ↑ My Hero Academia Manga and Anime: Chapter 77 and Episode 43.
|Forest Training Camp Arc|
|Chapters||70 • 71 • 72 • 73 • 74 • 75 • 76 • 77 • 78 • 79 • 80 • 81 • 82 • 83|
|Episodes||39 • 40 • 41 • 42 • 43 • 44 • 45|
|Battles and Events||Quirk Training Camp (Class 1-A vs. Pixie-Bob)
Vanguard Action Squad Invasion (Tiger & Mandalay vs. Magne & Spinner • Izuku Midoriya vs. Muscular • Eraser Head & Vlad King vs. Dabi • Tetsutetsu Tetsutetsu & Itsuka Kendo vs. Mustard • Katsuki Bakugo, Shoto Todoroki & Fumikage Tokoyami vs. Moonfish • Ochaco Uraraka & Tsuyu Asui vs. Himiko Toga • Bakugo Escort Squad vs. Vanguard Action Squad)