As My Hero Academia leads into the upcoming war between heroes and villains (which may or may not key into the series' finale), Shigaraki has been on a major tear for the last few arcs. As the series pitted him against many foes either more cunning or more powerful than himself, Tomura Shigaraki has been on a journey much like Izuku Midoriya's. He's been steadily getting stronger, and even reached a whole new level of power following the battle with Re-Destro and the Meta Liberation Army. But that's not the end of his growth.
After a tease that Shigaraki would soon blossom into a more powerful being than anyone could have ever imagined, the latest chapter of the series teases just how Shigaraki is getting there. It's a lot more gory than anyone could have expected as now it seems like he's undergoing some terrible experiments.
Chapter 255 of the series peeks in on Shigaraki's journey to become far more powerful, and it's revealed that he's undergoing experiments from All For One's mysterious doctor. The victory over the Meta Liberation Army and getting Gigantomachia to accept him as true successor was all the proof this doctor needed to grow him into the true successor to All For One.
As the doctor manically laughs, he notes that Shigaraki is an ultimate being with his "sense of self" intact that he and All For One have been searching for. As Shigaraki cries out in pain on an operating table -- with blood spraying from his body -- the doctor continues to cheer as his "masterpiece" is more perfect than expected.
All For One previously revealed that he was making Nomu out of a mutated curiosity as for how quirks work and evolve, and it seems like those experiments were merely a means to an even bigger end. This experimentation on Shigaraki teases that he will essentially become the perfect "Nomu," with all of his sense of self intact. This makes it even more tragic for Shigaraki, who is not groomed to be a successor but instead the final product of years of grotesque experimentation.
My Hero Academia was created by Kohei Horikoshi and has been running in Shueisha's Weekly Shonen Jump since July 2014. The story follows Izuku Midoriya, who lives in a world where everyone has powers, even though he was born without them. Dreaming to become a superhero anyway, he's eventually scouted by the world's best hero All Might and enrolls in a school for professional heroes. The series has been licensed by Viz Media for an English language release since 2015. My Hero Academia also launched its second big movie, Heroes Rising, in Japan this month.