the 1st time I see Kiriya is using pile driver i tot ... this is it..... full-throttle machine powered fighter. I quickly imagine he would be wielding some modified construction rivet gun (i dunno... i only see them in movies... it is hydraulic powered though). So, he would walk around while carrying a big ass hydraulic engine on his back while holding the big ass rivet gun on his shoulder or arm. Pretty much the image of Cyan Pile from Accel World.