Opening Thread

The Opening Thread (の) is an ability to guide the user towards an opponent's opening merely using scent. It helps the user align their Nichirin Sword's blade towards a demon's neck that defines the best place to slash that will behead the demon in a single swing. The ability is known to be used by Tanjiro Kamado during his battles with demons.

History
During his training with Sakonji Urokodaki, Tanjiro was taught that correct edge alignment in a blade is the key to a clean cut, making emphasis that any deviation or improper technique could potentially break the blade. Taking this lesson to heart when facing the Hand Demon, Tanjiro was able to detect a scent that he can follow to guide his Nichirin sword to his target's neck, allowing him to successfully decapitate it.

Tanjiro utilizes the Opening Thread in his battles with the Hand Demon, Swamp Demon, Yahaba, Kyogai, Rui, and Daki.

Usage
Using his extraordinary sense of smell Tanjiro is able to perceive the slight pause in an enemy's movement that creates an opening in which he can strike. The Opening Thread gives Tanjiro a path to follow in order to slice through the neck of a demon. He visualizes the scent as a thread that is attached to a demon's neck at an angle to give him a precise slash. Detecting it is often the most vital part in most of Tanjiro's early battles, as his fights with demons often involve surviving against their onslaught long enough to smell the thread for a successful strike and kill it.

While it gives Tanjiro a significant advantage to quickly gain the upper hand with a clear path to victory, the thread has a distinct and major flaw. Any change in his blade's direction or movement by a demon will cause the Opening Thread to "snap", forcing Tanjiro to look for another opportunity to attack and detect it again. Yahaba was able to snap the thread by disrupting Tanjiro's footwork on his path to reaching his neck, and Daki was able to snap it by moving too quickly for him to intercept and adapt to her new position.