WARNING: The following contains spoilers for My Hero Academia Season 5, Episode 10, "That Which Is Inherited," now streaming on Crunchyroll, Funimation and Hulu.
Izuku Midoriya is proving that shonen power scaling can be exciting again, breaking away from the trend of "born with a unique inner power" protagonists. Instead, Izuku was born Quirkless, but he eventually earned the right to inherit the incredible Quirk One For All. Even then, power still doesn't come that easily.
One For All is firmly in Izuku's hands, but that doesn't mean he's ready to throw a United States of Smash and obliterate his enemies with one titanic blow. That would be quite overpowered and My Hero Academia would get stale fast, so One For All comes with some baggage to keep it balanced and ensure that Izuku has a traditional shonen training arc or two.
One For All: A Superpowered Puzzle To Solve
All Might didn't just put new power into Izuku's hands -- he also handed down a complicated legacy, dating back to when All For One granted a Quirk to his sickly brother. Izuku is the ninth and possibly last user of One For All, and even now, after 98 episodes of My Hero Academia, he is barely scratching the surface of its true nature and history.
Such baggage prevents One For All from being a cheap and overpowered move from a narrative standpoint. It also creates compelling mysteries for the viewer, trying to piece together the Quirk's nature and lore alongside Izuku himself. How did such a unique Quirk come to be, and how can a naturally Quirkless boy like Izuku possibly master it? He has nothing but sheer willpower and some decent muscles on his side, but with any luck, that's all he will need.
From the very start, One For All has been a serious challenge, doling out little bits of power at a time and allowing Izuku to gradually scale up in strength. The aspiring Pro Hero received massive potential the moment he ingested that strand of All Might's hair, but unlocking it is the real challenge. Izuku was essentially handed a Rubik's cube, and he is twisting and turning it one move at a time to get the desired results. Or perhaps One For All's true power is sealed behind a door with many locks, and Izuku is painstakingly picking one at a time.
Izuku's Progress With One For All Thus Far
Izuku's progress has gone in fits and starts. Even in early My Hero Academia episodes, he was able to use a huge portion of One For All's power -- but at a terrible cost, which keeps this Quirk balanced and proves that great power comes with great responsibility for one's own health. Izuku nearly broke his arm throwing a baseball at 100% during the Quirk apprehension test, and when he fought Shoto Todoroki during the U.A. sports festival, he limited his use of One For All to mere finger flicks. Even then he was breaking bones, meaning he had "ammo" for the Quirk's power. This was unsustainable, so Izuku trained with Gran Torino to find a safer, more balanced use for One For All. Sure enough, this internship allowed him to remove a few more locks, using the Full Cowling technique and hitting safely with 5% power.
In case of extreme emergencies, such as when fighting Muscular, Izuku can go Plus Ultra at 1,000,000%. But the cost is serious, and he can't keep it up. One For All is wordlessly challenging him to find creative new uses for it, and now Izuku has yet another test: the Black Whip Quirk. During Izuku's fight with Neito Monoma's team, Black Whip manifested -- amplified with his own anger and One For All itself.
This terrifying new power will overwhelm him if he isn't careful, and he won't always have Shinso's Brainwashing ability to snap him out of it. Clearly, Izuku still has a long way to go before One For All is truly his to command.
