We are at final battle of the first macro saga from My Hero Academia. There doesn't seem to be room for much more fights now, so many kinks come to a head. However, Kohei Horikoshi has already made it clear that the series won't end here: numerous references to possible future events have been included.
In Chapter 284 of My Hero Academia, Deku decided to give everything against Tomura Shigaraki. The battle in the air that also led him to permanently unlock Nana Shimura's float quirk is under the watchful eye of the heroes and especially of Bakugowhich drew us into a look back a few months earlier.
In those past memories of when Deku was training hard to better learn how to fight in the air and use the black whip, Bakugo is embroiled in a conversation with All Might. During this chatter, the explosive boy mentions a note in the diary that the former hero had supplied with all the peculiarities he knew about the One for All and the previous owners.
While information about Nana Shimura and others was known, Bakugo noted what the fourth owner had been like first written and then erased along with its quirk. The thing is really strange, also because the expression of All Might caused quite a bit of confusion after Bakugo's question. The hero seems to know something but doesn't want to say it, probably for Protect Deku from a difficult situation.
What will that be original character of the fourth owner of the One for All? Maybe we'll find out in My Hero Academia 285, or maybe just in future manga arcs.