I hope its not something bad. It would be horrific for Shiba if he was part of Shadow Business.
I don't know. In all honesty Miura still hasn't had his big scene. He was presented as a good guy, that was keeping the class in check only with his charisma.
He was awesome, but then it kind of fell flat for him and he didn't serve a very big purpose.
Also, he's the only youth (part of the main characters) that never did anything bad for now..
There were a few panels, I don't remember in which chapter where we saw Miura or Katou, thinking deeply about something, but it never went anywhere.
And since I don't want him to be bad, I just hope, if he has anything to do with it, it's that it was his idea to stop shadow business.
On the other side, shadow business is basically what Katou did but on a bigger scale, so there might be a connection there.