The contents of the books are apparently very detailed and well-written, to the point of impressing even All Might after he took a brief look at the pages of one of them.
Izuku also uses this book to write down ideas for his own hero career, such as costume designs, combat strategies, and potential Super Moves. Izuku treasures these notebooks, as they contain years' worth of observations about numerous Heroes that he admires.
At the beginning of the series, Katsuki Bakugo had stolen, burned, and then tossed the thirteenth notebook away in front of Izuku, who had managed to retrieve it later. All Might also signed an autograph in 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 that the once weakling had an edge over him.
At the Sports Festival, it is revealed Izuku has documented the Quirks of all his classmates. A majority were shocked at the extreme detail he accumulated and rejected any help from the notes in their match.
- Izuku's current notebook is from the 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"). Notebooks one through twelve can be seen in the opening sequence for "THE DAY", and Episode 13.5.
|Technology and Other Objects|
|Support Equipment||Air Force Gloves • Amplifier Jack • Artificial Vocal Cords • Capture Tapes • Costume • Electromagnetic Soles • Eraser Goggles • Full Gauntlet • Hydraulic Bracers • High Density Weights • Hover Soles • Iron Soles • Jet Pack • Mid-Gauntlet • Quirk Amplification Device • Sevens Loud • Sharpshooting Gear • Wire Arrow|
|Weapons||Capturing Weapon • Capture Gun • Cement Gun • Claustro • Curious Flattener • Grenadier Bracers • Hyper-Density Seals • Taser Knuckle • Tiamat|
|Robots||Camera-Bots • Mini Transport Robots • I-Island Security Bots • Villain Bots • Kanidoge's Mechs|
|Substances||Quirk-Destroying Drug • Trigger|
|Vehicles||Allmobile • Hercules|
|Literature||Captain Hero • Hero Analysis for the Future • Meta Liberation War • Previous Successor Quirks|
|Miscellanous Objects||Provisional Hero License • Targets|