You've said this a couple times now, but I don't understand your point. This guy wasn't suicidal, he was delusional. He didn't try to commit suicide. He was a paranoid type who mistakenly believed he was being fired from his job. Japan does have a high suicide rate, 10th in the world, but most are over 50 and ill, and don't want to be a burden to their families. Teenager suicide is not significantly higher than anywhere else. Maybe you're trying to apply the image of US mass murders, such as the Va Tech and Columbine, to Japan?
I also don't get your teen angst point, either. This guy, and most people who commit murder in Japan, are not teenagers in angst.