I kinda relate to Sensei!
At first I thought you were saying you relate to the teacher and really wanted to hear your POV! 😂
I'm really not sure why Shuzo (is this an autobiography?) is so scared of this kid. I understand he's a bit brash but it doesn't seem like Hiromi is a horrible bully.
Yeah, I think it's his first time actually putting himself into a proper series rather than a character who's basically himself with a different name! But I don't think Hiromi is a bully at all -- just a first grader with behavioral problems. I just think that Shuzo and the others find him difficult to deal with. He seems developmentally challenged and he likely annoys and hurts those around him without realizing it. I don't think he scribbled all over Shuzo's drawings or punch him out of malice and he likely encouraged the teacher's investigations because he just wanted to draw.
Hiromi is the victim. Not just because Shuzo didn't speak up about the doodle. His fellow students probably find him just as annoying as Shuzo does and accused him simply they didn't want someone they liked to be punished. It could even be that the teacher put out her odd investigation specifically as a means of punishing Hiromi for his regular behavioral patterns in class because she expected only Hiromi to start doodling without given permission. More than that, we can see that Hiromi comes from a broken home. A tiny, dirty, shack, with miserable parents who barely care about him -- contrast that to the Oshimi household's upper middle class home.
I think Shuzo's guilt goes far beyond his sin of lying about the doodle but through a realization of what it means to see the victim (and perhaps one day even a friend) in that ugly annoying kid that pisses you off and to accept that Shuzo himself contributed to that coordinated victimization surrounding Hiromi. A psychological anguish based on one's own moral compass and inability to stand up for others.