I have to preface this by saying that the way in which Japan digests outside cultures and inject them into their mainstream from my viewpoint is problematic. Whereas with their own culture sports and art, they tend to spend the due diligence to perfect or become proficient, when it comes to outside cultural happenings, it is done very halfway or for either commercial or social gain. There are many things done in this country, as whole, because it is cool, but without proper context. There is also a certain level of hierarchy (big brother or do as older people say) that exists here and tends to get thrown on top of these things, which causes a lot of miscommunication, bullying, and unsafe behavior. It also brings down the level of play and the understanding of the sport, which can make playing dangerous.
That being said, this hit is not something that would cause such an uproar outside of Japan.It is a downside, but common part of the sport. I have definitely done worse on the muni, high school, and college level. I went out on the field to hurt people. At some point, I became good at it and was celebrated for it. It is a reason why I don`t really watch football or want Ito be involved with football as much as an adult.
Not to say that it is right what this player did. It was a dirty play, unsportsmanlike, and he should have gotten ejected from the game. He made a bad choice, due to pressure from his coach, and they both should be held accountable. Luckily I didn`t have coaches like that, but I didn`t really need them because I understood the game. What was to be done between the whistle and what was to be left for another play.