I don't disagree that the Japanese system wouldn't work in it's entirety here. I do, however, think it's reasonable that every gun be registered, that background checks be performed, that everyone who purchases a gun be required to take a firearms safety class (with periodic recertification), that certain psych diseases and being a felon should make you ineligible to purchase a gun, that the kinds of guns that can be purchased be limited, that the purchase of ammunition be limited, etc..
I also agree with your second point, that people can find a way to kill others if determined, as evidenced by the
stabbings of over 20 kids at a school in China yesterday (fortunately they all lived). At the same time, however, I think we should make it as difficult as possible for one person to kill many. Limiting who can own weapons and what kinds of weapons they can legally own is reasonable.