@Ryrie
He hit it several times, showing that normal hits didn't work. I would have tried spinning the blade once I figured out normal slashes weren't working. It isn't weird. It's putting though into it.
Hell. He STILL didn't think up anything on his own. He just happened to have a specific memory that literally handed him the answer.
@Riger in that fight he is highstrung/a bit of panic (because of the unknown), his mental state is like when you almost late to go to school/work but you cant find your motorcycle/house key anywhere.
For those wondering the phenomenon he describes with the mud is known as "shear thickening" you can try it out yourself if you have cornstarch. The faster you try to stir the solution the harder it will be and in some cases it can be so difficult that the solution seems almost solid.
The opposite is known as "shear thinning" where trying to cut or stir the solution/emulsion/suspension gets easier the faster you stir/move.
Finally an update yahooooo! Thanks for the update, please continue translating this manga really love it. Thank you translators can't wait for the next update.