@Human
This probably gets answered in the next chapter, but he is a white piece and he took out the black piece, right as it became whites turn. And as it mentions, you don't need to follow the orders of the king, meaning that its actually the first piece to move that gets to, which in turn made it no longer whites turn, meaning the piece that was attempting to take the turn to move, touched the fog
Sorry for ranting on, but that basically covers the entire situation
I'm just here for some good manhwa, feel free to suggest