Other than love, Deku's biggest weapon is a pen.
Deku has carried a pen and notebook with him for his entire life. Watching an AMV about him with the song "Non-Stop" from Hamilton the Musical (AMV link here, it's so good) made me realise something.
"How do you write like you need it to survive?" -> in Deku's case, it's not even an exaggeration - in fact, he DOES need to write in order to survive. Writing is like a survival mechanism for him cos he lives in a world where those with Quirks are the majority. A society that is built not for Quirkless ppl like him, but for this majority. Neither his world nor ours was built with minority groups in mind - thus, the survival mechanisms, as being Quirkless had always put Deku at a disadvantage compared to his peers. Even when he first received OFA, he was at a disadvantage cos he didn't have as much time to learn how to use it and so he was breaking his bones all the time.
Deku writes about his observations of the world he lives in, of the ppl around him, of the moves and actions of every pro hero, of all those that Hero society was made for, so that one day that info would be enough to put him at an equal level to all those ppl. So he could compete against them. He copies their moves in order to be in a better position. Everyone else naturally knows how to live in this society but Deku had to pick it up himself from birth. He had to LEARN it all himself, and through the accumulation of notes throughout his life, he's learnt.
With a pen, he turns knowledge into power.
