The USJ Arc was one of the first high-stakes story arcs of My Hero Academia. It was the first time Class 1-A's students were pitted against actual villains. It also established a lot of things that became important later down the line, including Kirishima and Bakugō's friendship, the Quirks of various students, and, of course, the League of Villains. It also helps give audiences a good first impression of what the bigger fights in the series will be like. This arc was jam-packed with great action and suspense, making it the perfect closer for the anime's first season. As such, there were a lot of big surprises that come out of this arc to throw readers through a loop.
To decide the arc's biggest plot twists, some rules will be observed. Twists will include plot threads that were expanded upon in later arcs even if they weren't made readily apparent within the arc itself; such twists will be chalked up to Kohei Horikoshi's careful planning rather than retroactive continuity. There are twists that can seem obvious to some but not as obvious to others, so they may be included, too. Twists will be considered based on how big an impact they have on the overarching story, but the real focus is on thier shock value. With these rules in mind, here are some of the biggest twists the USJ Arc had to offer.
The League of Villains' Arrival
At first, the USJ Arc seemed like it was going to be like the last arc. The initial premise of this arc was that Class 1-A would be practicing rescue operations in different types of disaster zones. If things had gone as planned, this would have been a decent, low-stakes arc for getting to know Deku's classmates and their Quirks. This still happens, but nobody expected they'd have to use their Quirks on actual villains.
What's really shocking about the League of Villains showing up is how early it is in the series. In the manga, this didn't even take 20 chapters to happen. In most Shōnen Jump manga, having the endgame antagonists show up to fight this soon is usually a sign that the series is getting axed. Thankfully, MHA's popularity meant that this confrontation would only be the first of many battles between the Heroes and the League.
Mr. Aizawa in Action
At first, it was hard to tell what kind of Hero Eraserhead was supposed to be. Nothing about him seemed like the charismatic figures shown on TV. This is apparently because he favors efficiency over media attention, but that didn't explain everything else about him. He had a disheveled look, he was constantly seen in a sleeping bag and he was very irritable. It was difficult to imagine him fighting crime.
When the League of Villains attacked, it was his opportunity to prove that he was Hero material in the field. Despite being greatly outnumbered and not having a Quirk suited for fighting multiple opponents, he was still able to hold his own and take down a good number of them. He also saved Tsuyu from being decayed by Shigaraki despite his own critical condition. Even if he didn't win, he showed what it takes to be a Pro Hero.
Deku Using One For All 5%
Deku's mastery of One For All was progressing at a really slow pace at this point in the series. At first, he had no idea how to use anything less than 100% of its power. As a result, he would constantly break whatever body part he was using his Quirk with. Thus, his strategies revolved around which body parts to break and when. Back then, using OFAl without breaking anything was nigh unthinkable.
The inability to use anything between 0% and 100% is what made Deku's 5% Smash such an unprecedented phenomenon. Not only that, but he wouldn't be able to use it again for another two arcs. As a result, he had to continue to rely on breaking his bones for the duration of the "UA Sports Festival" Arc. It came as a relief to finally see Deku take another step toward mastering OFA and not shatter his foot.
Shigaraki Not Being the Main Threat
As dangerous as Shigaraki looked, he wasn't the one to watch out for. At least, not in this arc. He was certainly a deadly enemy, the real "final boss" of the arc was the Nomu he brought along; it had power comparable to All Might, Shock Absorption and Super Regeneration. It seemed like nobody could handle this behemoth alone; even All Might needed to use over 100% of his full power to defeat it.
Shigaraki wasn't even the mastermind of the USJ raid. He was only the commanding officer. The real head of the League of Villains and Shigaraki's master was revealed through an anonymous phone call. This caller wouldn't be revealed as All For One until later in the series, but the message was clear; this was who was calling the shots. Dr. Garaki was also on the line, though he wouldn't be revealed until a later arc, either.
The UA Traitor
This isn't fully discussed in the arc itself, but there were several questions regarding the League of Villains' plan of attack. They were apparently certain that All Might would be teaching students and planned to kill him there with their Nomu. They even knew the precise time of the lesson and where it would be taking place. They were wrong about when All Might was going to show up, but they still knew too much.
It was concluded both in-universe and out that there was a traitor within UA. Whoever it was had to be leaking information to the League of Villains so that they could plan their assault accordingly. Fans would spend over 300 chapters speculating about who the traitor could be. They guessed everything from students to teachers to the principal. The repercussions of this traitor plot twist have followed MHA all the way into its latest arc.
