i try to avoid describing all might as a sort of MASK for toshinori because, well...it's just simply not true. to an extent. and i wanna elaborate on that a little bit because i'm just as confused as you.
up until here recently, i'd honestly say we've had a pretty even display of both all might and toshinori on screen. definitely enough to where we can see a pretty clear difference between the two. all might is LOUD, he's confident, he's present and makes his presence known β and above all else, he shows no fear. on the other hand, we have toshinori β who's more reserved, selectively confident and tends to air on the side of CAUTION when things start to get a little hairy.
now, there's a lot of characteristics that overlap between the two β like his optimism, amicability, and, unfortunately, his HUMOR. this is a much longer list than their differences, and that's due to one reason:
they are two sides of the same coin.
all might isn't a COSTUME toshinori puts on. all might isn't some alternative personality he uses for the cameras. they are not two separate people. all might is in every sense toshinori, and toshinori is, in every sense, all might β and, being foundationally built on the back of toshinori's core beliefs and values, he will never not be toshinori. the big guy is who he is because that's just who yagi was when he was younger, when he first started working as a pro hero, when he debuted as ALL MIGHT.
all might is not a mask because he's not FAKING anything. you wear masks to pretend you're someone or something you're not. he's not pretending to be all might, he's just putting on display who he was β who he still IS deep down. throughout the entirety of the 420-something chapters we have now, not ONCE has toshinori complained about the burdens of keeping up a persona β not once has he mentioned how it was all fake, how that just isn't him anymore or ANYTHING like what you see in most other shows and movies when talking about the heroic martyr. in fact, he really seems to ENJOY his time as all might. he enjoys his time on tv, he loves interacting with the community, he has literally stated how much of a JOY it is to be of service to others...that is what he claimed he was made for, that is what he continued to live for. and all might was the vessel he used to accomplish that.
which is what makes his story so TRAGIC in the end. because, when one for all started to decline with his health after his fight with all for one, he wasn't losing this person he was pretending to be β he was legitimately watching a piece of himself fade away as the embers slowly died out. and the less all might existed, the further apart toshinori grew from him β mentally AND physically.
at this point, it wasn't that all might was no longer toshinori β toshinori no longer believed he was all might, despite them still being the same person.
so what toshinori was TRULY doing, was using all might as a COVER, to hide the not so favorable parts of himself, the things that separated the two β his fears, his failures, his physical body that was clearly reflecting his declining health...all in an attempt to hold on to this other piece of himself for as long as possible. so he could continue to serve and have PURPOSE. because japan needed all might. the world still needed their SYMBOL OF PEACE...