Hero Analysis for the Future

Hero Analysis for the Future (将来の為のヒーロー分析) is a personal belonging of Izuku Midoriya, and is also the 13th of its kind.

Overview
Izuku uses this notebook to jot down his own analysis of Heroes (including the students of Class 1-A) and their Quirks, after observing them in action. The contents of the book are apparently very detailed and well-written, to the point of impressing even All Might after he took a brief look on its pages. Izuku also uses this book to write down ideas for his own hero career, such as Costumes, combat strategies and potential Super Moves. Izuku treasures this notebook, as it contains several years' worth of observations about Heroes that he admires.

At the beginning of the series, Katsuki Bakugo had stolen, burned and then tossed this notebook away in front of Izuku, who had managed to retrieve it later. All Might also signed an autograph on this notebook after saving Izuku from the Sludge Villain.

During his mock battle with Katsuki, Izuku is revealed to have memorized the contents of the books which he told Katsuki who recalled the book and was angry his rival had an edge over him. All Might is revealed to have read the book when he saved Izuku and was impressed he put his knowledge to good use.

Trivia

 * Izuku's current notebook is from the Kokuyo Campus Note notebook brand (changed to "Campos" and "Kukuyo" in the main series)
 * Izuku has, or at least had, multiple notebooks, as the one used at the start of the series had a numerical identification (in this case, "No. 13"). Brief images of notebooks 1-12 and their covers can be seen in the opening sequence for THE DAY, and Episode 13.5.