Niryūgiri

Niryūgiri (二流斬り, Niryūgiri; literally "Twin Flow Stroke") is an Iaidō technique.

Overview
Utilized as a following through maneuver for when a standard unsheathing slash, found commonly in the Iaidō style, the swordsman keeps their left hand (or right) firmly held against the top of the sheath while drawing their sword with their right hand (or left). Upon drawing the sword to strike the target at incredible speeds, one must always consider the possibility that their slash, swift as it may be, could possible be parried or even avoided by a skilled adversary. Therefore, this technique was created in order to deal a follow-up strike by using the sheath itself, being drawn and held in an icepick manner, which follows the motion of the body's momentum following that initial strike. This is a two-step technique that takes advantage of the element of surprise, as many opponents would never expect to have an adversary that would actually use their sheath in combat.