It's pretty cool that we can now refine extra 5* ninja fragments. I think this is a permanent addition in this game, but please do correct me if I'm wrong.
However, someone posted in future there should be a skillbook feature where we could upgrade our existing ninja skills with fragments. Is it true? Should I hold onto my fragments then, especially on main character?
I remember a picture was also posted as an example, showing kakauzu's chase skills doing ignition and paralyze after upgrade.
Also, can we do selective refinements here? Like, I want to keep all extra fragments of my main character, but use all guy and hinata fragments. Can I do that?