Warning: contains spoilers for My Hero Academia Chapter 335
The long-simmering traitor arc in My Hero Academia is finally coming to a head, and the treasonous hero has turned out to be someone that fans wouldn't look twice at.
The "U.A. Traitor" theory has been floating around since the manga's U.S.J. arc, which took place in chapters 13 to 21 of the manga. After the villain incursion into the U.S.J. training facility and the press's invasion onto school grounds, some faculty at the school began to suspect that there might be a traitor working for the League of Villains among them. This was only reinforced for Present Mic at the Forest Training Camp arc, where he points out that only those who were present at the camp knew its exact location, implying that the traitor must be in class 1-A, 1-B, or among the faculty escorting them. But since no further leads emerged, many fans were wondering if the plotline had been forgotten, and even some characters decided that after moving into the dorms, there couldn't possibly be a traitor.
All of that changed with the end of Chapter 335, however. As All for One illuminates Dabi on his backup plans, he mentions his "Friends," and the image behind it is of the Invisible Girl Toru Hagakure, a student in class 1-A and one of the least developed and least suspected of all students. My Hero Academia has often struggled to give other hero students their share of the spotlight, particularly as Bakugo and Todoroki rose to become the deuteragonists alongside Midoriya. Many, like Momo, Iida, and Uraraka have still had some time in the sun, but others like Koji Koda, Rikida Sato, and Masahirao Ojiro haven't, and Toru definitely lands more on that side of the fence. Many of these characters have been discussed as possible traitors, but none more so than Aoyama, who was said to have been accidentally revealed at an art exhibit in Japan several months ago.
When All for One refers to someone as a "friend," it usually means that person owes him a favor, but what Hagakure might be getting from All for One remains a mystery. Since one of the earliest favors All for One is shown doing is taking someone's quirk away, it's possible that Toru simply wants to get rid of her invisibility quirk and live a normal life. Toru Hagakure's true appearance has never been seen, since her quirk is always active, so only the form of her body in clothes is ever visible. It's also the perfect quirk for a spy, since all she needs to do is remove her shoes and gloves and she's completely undetectable. She could be sitting in on every meeting that the faculty of U.A. have had, and they'd never have a way to know it. And since she's invisible, it's rare that she's noticeably present even in group shots, so it's easy to slip away without being noticed. During the Forest Training Camp attack, Hagakure was "unconscious" from the gas, providing her cover to slip away and meet with the villains.
U.A.'s faculty was already on high alert due to fears of Himiko Toga sneaking in while disguised, so it may be trickier than usual for her to get in touch with the bad guys. What exactly all this means for My Hero Academia's rapidly approaching ending still lies ahead, but the betrayal and confrontation that await Hagakure's classmates is sure to be a heartbreaking reveal.