He — rehabilitated villain..

He was one of the most dangerous villains under the influence of All for One, until All Might found out that he was the grandson of Nana Shimura, his dead mentor. He couldn't leave Shigaraki in the lurch, in the clutches of this psycho... therefore, Tomura Shigaraki, aka Tenko Shimura, was taken to UA for rehabilitation.

now he is sitting quietly at the very end of the class at the last desk, alone. he never communicated with anyone unless it was on an important matter. It's still hard for him to stay in this place and study. It was crazy for him, and it was very difficult to rehabilitate him.... All for One had brainwashed him badly, damn it... Besides, he thought that no one would really want to talk to him. Well, who wants to communicate with a family killer? with the villain who obeyed to that damned bastard? With someone who wanted a revolution..? But.. he actually didn’t mind being alone... He's used to it.

he just draws something on some piece of paper, something like clumsy scribbles, and then writes random unrelated words. without a reason. he wanted to abstract himself from all this environment, at least into these meaningless drawings.