"Hanauta Sancho: Yahazu Giri" is one of Brook's most iconic and powerful techniques in the One Piece series, literally meaning "Three-Verse Humming: Arrow-Notch Slash." Being a very fast attack, Brook puts on quite a fantastic display of his mastery in both areas: swordsmanship and music, making it one of the strongest in his arsenal of moves.
Brook performs Hanauta Sancho: Yahazu Giri with his signature sword, Soul Solid. Soul Solid is a cane-sword that Brook wields with exceptional mastery. This involves Brook quickly moving towards his enemies and executing a flash slash so fast that the enemies are not aware of being slashed until some moments later. In fact, this delayed realization is one of Brook's hallmarks for his precision and speed, showing that he can outmaneuver and outspeed an opponent.
Brook, once a battle leader for the kingdom where he was born, also provides a strong background for the execution of Hanauta Sancho: Yahazu Giri. This technique is said to be the fastest cutting move among that kingdom's assault squad, so Brook definitely was an elite swordsman before entering the Straw Hat Pirates.
Visually, the technique is often represented with Brook almost disappearing from view because he is so fast, and then a clean, quick cut afflicted using Soul Solid. The grace and fluidity of the attack mirror Brook's combat and musical grace, fluidly fusing his abilities into one single devastating technique. This visual presentation is dramatic and engaging, making it memorable to fans.
The name "Hanauta Sancho: Yahazu Giri" suggests a lot by itself. "Hanauta" actually means "humming," so in that sense, it reflects Brook's musical background and his tendency to blend music with his fighting style. "Sancho" literally means three verses, and thus it would mean succession or a triad of things, while "Yahazu Giri" translates as "Arrow-Notch Slash," implying sharpness and precision connected with the technique.
Brook has visibly used Hanauta Sancho: Yahazu Giri many times across many arcs, thus proving the skill prominent in his arsenal of combat. Among these instances is the Thriller Bark arc, where Brook uses this technique against a myriad of threats that surround him alone, showing his agility and great swordsmanship. This speed and suddenness of the attack catch the opponents off guard, thus defeating them quickly.
This technique further outlines Brook's strategic and adaptive way of fighting. Even with a skeleton appearance, his power is backed by the Logia-type Devil Fruit, Yomi Yomi no Mi, that granted him rebirth into a physical form with added abilities. Through his skeleton body, his movements became lighter and faster, hence easily performing a high-speed technique like Hanauta Sancho: Yahazu Giri.
This can further be noticed from the fact that Brook often hums or sings while making an attack. Thus, combining the musical elements with his fighting or brooding techniques seems to be what characterizes Brook from other swordsmen of the One Piece world.
Brook, throughout his development in the series, closely links techniques such as Hanauta Sancho: Yahazu Giri. Be it from his resurrection and eventually joining the Straw Hat crew down to all the battles in which he has fought, Brook has always been a growing, versatile warrior. Such a technique symbolizes how the past he experienced can be harmonized with the current role he had to take up: fusing his history as a musician and leader into his new life as a pirate.