Very hard puzzle

Retract the black rook, that frees the king, which frees the knight, which frees the bishop

Technically it's not my solution, it's CM JamesColeman's. I just volunteered to post an explanation of his solution since we discussed it for a bit.

But either way, we might as well discuss how ALL the pieces ended up in their positions, which is pretty difficult considering the solution comes from the assumption that both sides were not playing accurately. So far, this seems like the most likely pattern of events to have occured to have the end position in the puzzle.

I went a little further, but I suppose this is a method the bishop ended up on h3. But again, it's difficult to tell for sure.

Or you could play monster chess and go Kg5-f5-e5