Yuga Aoyama turns out to be U.A’s Traitor - Anime Theories that Turned out to be True

We all had our doubts over Yuga Aoyama but simply ignored the possibility just for him not having enough watch time. However, Chapter 336 of My Hero Academia shocked us by revealing that Aoyama was indeed the traitor who fed All for One every vital intel from U.A. 

The chapter also revealed that Aoyama was born without a quirk, but his parents resorted to All for one’s powers to implant a quirk into him. This explains why Aoyama’s naval beam had a damaging effect. It wasn’t Aoyama’s quirk, to begin with, so naturally, his body rejected it. Now, everything comes at a cost, and All for one forced him to infiltrate U.A as a payback.