WARNING: The following contains spoilers for My Hero Academia #257, by Kohei Horikoshi, Caleb Cook and John Hunt, available now from Viz Media.
During the Joint Training Battle, Izuku Midoriya unlocked Blackwhip, the Quirk of former One for All holder, Daigoro Banjo. Although the ability has proven somewhat difficult to control, Deku is now relatively proficient with it, although nowhere near the level of his teachers. However, Blackwhip was only the first of the Quirks that Deku will unlock, as all the powers of the former One for All holders are now flowing into him. In My Hero Academia #257, All Might reveals Midoriya's next Quirk: Float.
All Might brings Katsuki Bakugo and Midoriya into a meeting to explain what he knows about One For All's previous users. After Bakugo doesn't recognize the names of the former holders, All Might explains All For One used his incredible powers to go around destroying the powerful. This means, for the most part, the previous holders of One For All just focused on passing their abilities on, and as such "they all died young."
The former number one hero then reveals Midoriya will soon learn Float, which was the ability of Nana Shimura. Despite her death, Nana has played a pretty central role in the series behind-the-scenes. She's both All Might's mentor and the grandmother of Tenko Shimura/Shigaraki Tomura, the incredibly powerful leader of the Paranormal Liberation Front.
Although a lot of details about the Quirk are unknown, Float allows its user to, well, float. Despite the fact the Quirk will definitely power Deku up further, Bakugo immediately mocks the ability, explaining his blasts already allow him to fly. Midoriya then gets determined to master the Quirk faster so he can catch up to his rival. Bakugo's mocking is right, though. Midoriya's Float quirk is a little redundant. In addition to many heroes being able to fly or leap tall buildings in a single bound, Ochako Uraraka's Zero Gravity Quirk is basically just a more powerful version of the move, since it allows her to make most things float.
However, the power of this new Quirk isn't just in its practicality. Float belonged to someone integral to All Might, and seeing Midoriya tap into his old master's power clearly affects him. After the meeting, Aizawa finds All Might sitting outside in the cold, frustrated he can't do more for his students. The relationship between All Might and Midoriya will be affected by the latter gaining Float and the symbolic meaning of inheriting the power of the person who trained him. This will certainly inspire All Might more than ever to make sure Midoriya becomes worthy of One For All and becomes the kind of hero the future needs.