So, I'm bored and I was thinking if I am allowed to return to this game. Do I really need to be caught up in all that's happened?

With the way Shiro was written, as cheap as it can be, his Semblance gives me a literary loophole that is essentially a "reset" button. It's as simple as Shiro having been part of some mission where he did a reckless thing that ended with him in a coma. Waking from it in IC to either little or large fanfare.

The drawback of course being any character development and memory all being wiped clean.