@mtt @gomichandesu
It depends on the crime. Murders usually get full coverage, a recent example would be the murder of Uemura Ryouta in 2015, where the news published his name and the details just a few days after it happened. Here is the link for his wiki article: https://ja.wikipedia.org/wiki/%E5%B7%9D%E5%B4%8E%E5%B8%82%E4%B8%AD1%E7%94%B7%E5%AD%90%E7%94%9F%E5%BE%92%E6%AE%BA%E5%AE%B3%E4%BA%8B%E4%BB%B6
And as you can see, the police only hid the identity of the murderers (A, B and C) in order to protect their family. The internet can be quite agressive towards them, sending death wishes to the family members because "a rotten apple comes from a rotten tree". There is a movie which centers around this plot, a detective needs to protect a little girl from the media after her older brother murdered someone and... yeah, people can be nasty. The movie's title is 誰も守ってくれない or Nobody to Watch Over Me if anyone is interested.