The society and operation against criminality makes no sense whatsoever. If your setting isn't believable, I am taken out of the story.
Tags determine whether you are a killer because your name changes colour to red if you kill someone with a tag. But also you are not required to have a tag... It is entirely optional. Also you can take your tag off at any time and if you do your crime will not be reported. There is no real benefit to keeping the tag constantly equipped to counterbalance that.
It's like someone read SAO and thought the criminal system was cool but didn't consider the actual implications and implementations for such a thing.