My Hero Academia's big spin-off Vigilantes has been opening our eyes to hero world of Kohei Horikoshi's main series as it shows a new side of it from several years before the main series begins. This has led to some significant tie-ins with the main series, and even had a crucial bit of back story explored through a special arc about Aizawa's past at U.A. Academy before he became a hero. But while there have been several notable heroes making their appearances, it hasn't been the same for the villains as the spin-off has generally been evolving its own villainous roster.
That's all changed with the latest chapter of the series as it fills in a crucial piece of Knuckleduster's past as the speedy hero O'Clock, and as Chapter 75 of the series reveals, it turns out that Knuckleduster once had an intense run in with All For One. This also explains why his speedy quirk is now in the hands of the villain Number 6.
In a previous chapter of the series, it was revealed that Iwao Oguro used to be known as the pro hero O'Clock. His Overclock quirk, which allowed him to speed up his body to supersonic speeds, was stolen from him and eventually set him out on the path to becoming the vigilante known as Knuckleduster. In a letter to Koichi in Chapter 75, Iguro reveals this past to his former pupil.
In Chapter 75, he reveals he became such a good hero that he learned to work within the system and was completely flabbergasted when faced across a monster beyond his understanding, All For One. This explains why his quirk now resides within the villain Number 6, as All For One has the ability to steal quirks and implant them within others. This connection also explains why Number 6 has access to a prototypical Nomu as All For One most likely is using Number 6 to further his own goals.
Now that All For One's fingerprints have been put on the spin-off story as well, now we'll see if there are any further connections to the main lore of the My Hero Academia universe. This could be part of his grand scheme, but what do you think?
Surprised to see All For One make an appearance in the spin-off? Do you think he'll show up in Koichi's future? Let us know your thoughts in the comments or talk to me directly about all things anime and other cool things @Valdezology on Twitter!