WARNING: The following contains spoilers for My Hero Academia Chapter 338, "The Story of How We All Became Heroes, Part 1” by Horikoshi Kohei, Caleb Cook, and John Hunt, available now in English from Viz Media.
Fresh after the reveal of the UA traitor, My Hero Academia continues to prove that it's not yet done with the surprises. While Class 1-A debated Aoyama Yuga's fate with the police department and UA staff, Aizawa Shota, Class 1-A's beloved homeroom teacher and fan-favorite character made his reappearance, and he's hiding a pretty big secret.
The previous chapter ended with Midoriya Izuku extending a hand of forgiveness towards Aoyama. While it seems like finding out he was the UA traitor won't cause any rift between Aoyama and Class 1-A, he won't be able to rejoin them immediately. Detective Tsukauchi noted that he still couldn't be completely trusted. He'd collaborated with All For One after all, and they still couldn't completely rule out the possibility that he was booby-trapped in a similar manner to Lady Nagant.
As the Aoyama family's interrogation continued, they found out that their communication with All For One was always initiated from his end: He'd only approach them if there was information about UA he was interested in. Attempting to bait him with false information would be difficult but, as Kaminari Denki noted, not impossible. Yaoyorozu Momo also pointed out that the only person capable of deceiving All For One at this point might be Aoyama, and he was overwhelmed once again by his friends' unwavering trust in him.
It was at this juncture that Aizawa finally stepped in. He wasn't physically present as he was likely still recovering from injuries received during the Paranormal Liberation War, but he was all caught up as he'd been listening in via video call. He revealed that he had no intention of expelling Aoyama from UA and that he shared the same sentiment as his students. However, like the detective, he acknowledged that it would be unwise to fully trust the Aoyama family just yet and asked that their ears be covered as he revealed his plan.
While Aizawa's plan hasn't been revealed to the reader yet, the characters' expressions after hearing it belie its merit. It doesn't seem like one that will guarantee success but, according to Principal Nezu and Detective Tsukauchi, it's feasible enough to try. They wasted no time in beginning preparations towards it, which involved the inspection of "each and every location" possibly referring to UA's grounds. The first-year students returned to their regular training regimen.
Aizawa wasn't the only character that made a surprise appearance. As part of Midoriya and Iida Tenya's preparations, they headed to UA's support department for repairs and upgrades to their hero costumes. There, they ran into Hatsume Mei, the support item genius and an old comrade from the Sports Festival. Her reappearance teases more epic additions to Midoriya's newest costume. Given how much more he's capable of now, Hatsume will definitely be able to capitalize off his new abilities and create useful tools for both him and Iida. Should she be able to repair his Mid-Gauntlets, Deku will once again be able to increase the percentage of One For All that he can comfortably use.