Good manga with a solid scenario.
Also a good warning, considering nowadays with the shadows online market it's possible to get explosives without being noticed, as long as you have nothing to loose.
I was someone who spent nearly a decade being mentaly abused by basicaly the whole school, especialy in middle school, being called "virus", "stinky", "poisonous man", "fucking nerd", "die-a-virgin", etc. Not physically, tho , since the only time someone tried, I sent him to the infirmary. But every single day, at least two or three random students would just insult me out of the blue. Finding my bags in the trashes had become a routine, to the point the school comitee had to lend me a safe for leaving my school supplies on. There were signs of trying to force the locks, so I had to find the janitor several times a month to break the padlocks and bough them in pack. Also, people found it fun to test their knifes sharpness on my bag.
I have been on my own for most of my life. And the worst of it, I think, was that the school never ever took real measures to stop the shitty mentality of the student. Sure, when I pinpointed the phone numbers that a bunch of bitches used to spam me for fun u with random insults when somehow they found out my phone number, they got 'formal warnings', but that's about it. Some dude trashed your bag ? 'Formal warning'. Some guy wrote insults on your desk? 'Formal warning'.
I was even more or less encouraged to cease any proactivities by the school that I did on my own. For example, some idiot student found out the Youtube gaming channel I did back then, and of course I got stormed by insults from people from my school, always mentioning my real name. And in the following days, I'd get convocated by my fucking school commetee to be informed I was not authorized to mention the school name to my fucking content!! Translation: "You makes a bad buzz, stop your channel because you could make bad publicity for the school."
Another time, some arabic dude even got to the point of going to the student comitee to tell them I said racist insults to him. This dude was filled with records of bullying up all his ass, but they still believed him and I got to write a fucking apology letter to the same guy who, the very day before, insulted me for 30 minutes on a bus along with 10 others people, to the point the bus driver menaced them to call the cops.
And, as the manga states, they didn't do that for a reason. They do it for fun. I had a different mentality than them, so I supose my very existence was a crime to them.
My point is, I can clearly tell you, you can clearly drive the most sane person to do the biggest attrocities. Simply because humans are animals that reproduces the behavior of the other. In my case, I managed to vent out all my anger from the bullying aways by playing videogames, reading (sometime writing) books, drawing and the like, but I cannot deny I felt extremely good when I could do the school comitee job and pinpoint enough evidences of a bunch of students to get them suspended.
No wonder some people with more anger management issue end up shooting people from their school.