That said, I think people need to recognize that in many aspects what's happening is connected to societal issues that gun control and gun regulations will have very little impact on - remember, even in Japan somebody could make some kind of battery ignited home-made shotgun and kill Shinzo Abe.
Countries with strict gun control enjoy far lower rates of firearm accidents, suicides, and murders. IMO it's clearly worth the tradeoff. Very few of us live in a place where only guns can solve our problems.
The fact that occasionally someone goes to great lengths to kill doesn't mean we should make it easier for everyone.
Japan is, famously, a country where the system generally works. Hell, a late train would get you a letter for your boss. It's a bit different in places where the police don't have the resources, or dangerous individuals aren't removed from the public.
Yemen is in second place for guns per person. How responsive is their government to the people?
The debate over guns actually hinges on the extent to which the individual should be empowered to defend themselves, and historically, it hasn't just been about guns, but about all weapons, and even martial arts (which have also been banned at various points in history). Governments don't like to empower the individual, because they want to maintain a monopoly over violence (for many practical reasons), and because empowering individuals often creates its own set of trust problems (which is true for anything -- how many drivers are trustworthy, for example). Defenseless individuals are easier to govern from an administrative perspective, and if a government is good at protecting the populace from threats, it works. In fact, it can be better for the population as a whole, at least while the government is competent. But life is messy, and there are points where individuals need to defend themselves. As systems break down, not only does the need increase, but also the effectiveness of the means, because the threats you have to defend yourself against by definition don't play by the rules.
This, imo, is the real point of the second amendment. The Bill of Rights is essentially a declaration that certain rights are derived from a higher authority than government, which is why they are inalienable. No one needs permission to defend themselves, and it's my belief that the right to bear arms was put in there to ensure that should the system fail or become ineffective, the people would still be able to exercise one of their most fundamental natural rights. It certainly wasn't an accident, because it was the second thing that they added. The verbiage around government and militias makes sense in the context of having just fought a war of independence, but it also makes sense when you consider that it's often well-meaning governments that take this right away.