Was uzuki or the gang arrested at all? If not that's a shitty police and a shitty investig...

Since it was just property damage if the "victim" Chika's grandpa doesn't pursue, I guess they can't make arrests. Also they are middle schoolers, even if they did get in trouble I don't think property damage would translate to jail time for them. Plus, the police were biased against Chika if Gen did want to pursue a case, the police might have dragged Chika through the mud first since they hate him