You would know more about this than I, but everything I have read or heard about Japan has noted the high degree of civility in that culture. There is respect for others and an etiquette not practiced much in U.S. I think that is how Japan can be so congested in terms of population and still not have the people turning on each other.
Contrast with U.S., where increasingly there is much under-parenting of children and little regard for others (Not always this way -- I recall that my neighbors would tell me not to do things, not just my parents, and I would abide. Today, if you tried to tell a child not to do something, the kid would likely tell you to "F___ Off!", and the parent might then come to your door with their own choice words and ready for a fight: "Don't you tell my kid what to do!").
In Japan, it appears that controls upon the individual's demeanor and behavior are internalized, such that when the govt forbids firearms, the populace understands this is for the common good, and most abide by it and don't try to obtain weapons illegally. In U.S., control is not internalized, and only external controls (laws, police) have much hope of working. The common view here is, "It is only illegal if you get caught." So, a proposed ban on weapons in U.S. would first be opposed politically, and then if it were enacted, persistent attempts would be made to get weapons anyway. To some, it would be a challenge to see how many illegal weapons they could bring in in defiance of the law.
Gun violence hasn't lead the majority of Americans to think that guns are the problem. Actually, the opposite has occured: The more violence we see in the media, the more convinced Americans are that they must also arm themselves to respond to it -- you don't want to be the only one in a dispute without a gun. Increasingly, women in U.S. are purchasing guns and being trained in their use, so that if need arises they can blast the bad guys. Can you imagine that viewpoint among citizens in Japan?