I think there are two things here: first is that Japan is so safe that police is actively looking for cases to pursue. I remember reading of police putting (as a trap) a case of beer in an open car at a shopping plaza, monitoring it for a week before finally nabbing a retiree who opened a door (whether to "steal" the beer or just to investigate). In and of itself such safely is, IMO, something to celebrate.
The second is that the justice system is structured so that the state is always right and the criminal system famously has a conviction rate that exceeds 99%. Couple this with the vaguely defined laws (as cited in the article) and the desire by police to find some criminals, somewhere, and the results can be ugly. Dangerous to the bystanders at best, enabling local dictatorial powers at worst. My 2c.
The second is that the justice system is structured so that the state is always right and the criminal system famously has a conviction rate that exceeds 99%. Couple this with the vaguely defined laws (as cited in the article) and the desire by police to find some criminals, somewhere, and the results can be ugly. Dangerous to the bystanders at best, enabling local dictatorial powers at worst. My 2c.