Whoa, tell me more about Demon Splitter II.
I think Shiryu's awakening will allow him to escape practically all 5 senses completely, which means not even FS would work since it is basically a "sight", making him and all his attacks virtually nonexistent. So, fighting him is like fighting Nothingness itself, because his targets will not even register his attacks long until after they have been inflicted. Add to that the predicted Jozu's diamond df to his sword, we hark back to Zoro’s flashback about cutting nothing at Arabasta and cutting diamond after he won against Mr. 1, and there you have it.