Japan is actually not the safe haven you guys imagine it to be. I'm pretty late to the party, so I'll keep it brief. Even though Japan might look really safe on the surface, there are lot of things going on in the underground of the society, such as yankees and yakuza, and police generally don't get involved unless there's a serious crime involved. I have a friend who used to live in downtown shinjuku and apparently the area is loitered with yakuza.
There's also the case of bullying in Japan, which for some reason is being encouraged by the teachers, which sometimes (if not often) escalates to physical violence.
These things in Japan are not taken as seriously, and even though it is beginning to change, it's still pretty bad atm.