For the OFA are assassins AU.
Some of the techniques used would probably fit underground heroics. The stealth and fighting techniques.
So Aizawa might take a certain interest into Izuku. Might wonder how he learned about it.
Imagine his surprise when he finds that All Might who is not really subtle thought him that.
Aizawa doesn't like All Might and he's always thought the smile was fake, but like. He thought it was hiding an idiot, or someone who just wasn't actually as nice, or a glory hog ego just wanted praise. He did not expect an assassin, he did not expect someone who could do his own job better than him! Izuku would be a great student, and I hc that underground learning tends to be communal anyway- but how is he supposed to broach the subject when All Might is the one who taught him that much? Is All Might going to take the attempt as one to poach his student? He knows erasure isn't going to stop a knife in the back or poison
