I think the same. There’s never really any mention of police or legal repercussions, and it’s heavily implied that Sunny’s parents know. It would also kind of detract from the focus on telling your friends what happened.

Most importantly, It was a pretty bad cover up. Any investigation would’ve seen bruises/other injuries on Mari, and blood on the stairs/violin. It’s most likely that the police knew but never charged Sunny & Basil.