Japan is safe for four main reasons.
Japan is much more ethnically homogenous. Racial tensions are tiny compared to the U.S.
Japan is much more economically homogenous. Income differences are very small compared to the States. This leads to less jealousy and incentive to rob/steal. CEOs don’t take multi-million dollar bonuses when the company is in trouble. This is closely related to the third reason…
Group mentality is emphasized over the individual. This has its down side but it works wonders for creating harmony in school, the work-place, and in times of disaster.
No guns. Actually, you’re not even allowed to walk around with a knife in your bag. Straight to jail. People argue that having a gun keeps them safe. But if you need a gun to be safe, you’re not in a safe place.