(I was bored and had an idea, EVERYTHING BELONGS TO Kohei Horikoshi!!!) Deku had his notebooks full of hero notes, yes. But he had 13 of these books, they couldn't just be analysis. No, some of these books were full of journals and poetry, that helps his cope with his problems. From his mother working constantly and rarely seing her, to his lack of quirk and friends, and then to the bullying. This book was what kept his sadness at bay. (I'm horrible at descriptions. There may be dadzawa)