The Nipponese don't go in for this nonsense about follow-through. If you strike a man on the top of his head with a katana and do not make any effort to stop the blade, it will divide his skull and probably get hung up in his collarbone or his pelvis, and then you will be out there in the middle of the medieval battlefield with a foot on your late opponent's face, trying to work the blade loose as his best friend comes running up to you with a certain vengeful gleam in his eye. So the plan is to snap the blade to a full stop just after the impact, maybe crease his brain-pan an inch or two, then whip it out and look for another samurai, hence: "Next!"