If they reach full strength, things will get worse than ever which is why I have to stop Shigaraki and All For One before that happens.”Clearly, Izuku has his head set on saving the country all while keeping everyone safe.
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He is the kind of person to put others before himself, so this selfless decision comes at no surprise. It seems Izuku has been busy during his solo period, and his powers have grown considerably. So if My Hero Academia fans are lucky, he will be reunited with his Class 1-A allies before too much longer.