Yoru is an ornately decorated and very long blade with a total length of at least 7 feet, as it is seen to be at least a full head taller than Mihawk himself (who is 6'6", or 198 centimeters) when it is placed on his back. On the hilt of this blade is a crossguard, though the bars between the blade and the hilt are much longer than average. The blade itself is pitch-black with a very strong sheen, and its shape is similar to the German "Großes Messer", a single-edged long sword with a slight curve at the end of the blade. Overall, Yoru looks like a large black cross.
Mixed with Mihawk's abilities, Yoru has tremendous power, as it was seen destroying Don Krieg'sflagship with a single strike. While Yoru is the sharpest blade in the world, it is also gentle. This was as demonstrated when Mihawk deflected the course of bullets that were aimed at him with only a slight touch of the sword. He can also launch a massive slashing attack of compressed air or energy that can reach at an extremely long distance, sending spiraling waves at the opponent at pinpoint accuracy, and capable of slicing a mountain of ice from afar.
Although Mihawk does not name any of his attacks in the mainstream of the series, there are several specific attacks he has used during the series that are named in various video games. Below is a description of the variety of attacks shown.
Mihawk swings his blade to launch a wave of compressed air from his sword, which is able to cut everything in his path, making a powerful long-range slice. A vertical version of this attack was first seen to cut in half Don Krieg's ship and a horizontal version was then seen in attempt to attack Luffy, but missed, slicing a massive mass of ice instead. This is called Kokuto Issen (黒刀一閃,Kokutō Issen?, literally meaning "Black Blade Single Flash") in Gigant Battle.
The Strongest Slash of the World (世界一の斬撃,Sekai Ichi no Zangeki?): It is an extremely powerful technique, possessing incredible range and power. Because a marine in the manga calls it "the world's strongest slash", people often mistakenly think that it is Mihawk's strongest technique. However, a more accurate translation shows that the marine simply meant that it was a slash made by the world's strongest swordsman. Using his Yoru, Mihawk launches a massive air compressed wave (even longer than the Moby Dick) towards his opponent, capable of cutting through massive amounts of ice, and supposedly much more. "Diamond Jozu" of Whitebeard's crew was able to stop it, although it's unknown if it was because Mihawk lacks the ability to cut through diamond, because Mihawk did not expect Jozu blocking the attack or because of the use of Haki on the part of Jozu. It was "named" by one of the war participants when he described the attack, when used as a long-range opener against Whitebeard but was blocked by Jozu's diamond body; in the anime, it was able to force Jozu back a distance.
Mihawk jumps, standing on his sword, and descends to impale his opponent. It was first seen being used against Luffy. This is called Kokuto Arahoshi (黒刀荒星,Kokutō Arahoshi?, literally meaning "Black Blade Heavy Star") in Gigant Battle.
Mihawk awaits his opponent's next attack holding his Black Blade with two hands over his back. Once the enemy attacks, Mihawk counterattacks quickly with a powerful downward slash. It was first seen attempting to be used against Luffy's Gomu Gomu no Jet Bazooka, but thanks to his awakening Kenbunshoku Haki, Luffy realized that if he attacks Mihawk, his arms would be cut off and thus directed his attack to the ground, making Mihawk unable to counterattack. This is called Kokuto Saku (黒刀朔,Kokutō Saku?, literally meaning "Black Blade First Day") in Gigant Battle.
Mihawk attacks with his Yoru at great speed. This technique seems to be more powerful than a normal slash of the sword as it emits some kind of cutting air (but not enough to cover great distances). This was first seen against Luffy. This is called Kokuto Kogetsu (黒刀弧月,Kokutō Kōgetsu?, literally meaning "Black Blade Arc Moon") in Unlimited Adventure, Unlimited Cruise, and Gigant Battle.
Mihawk makes a downward swing to launch a projectile of slicing wind that travels at great speed through the ground. This attack is able to cut through steel with ease and rapidity. It was first seen used against Luffy but was blocked by Mr. 1, who receives all of the damage instead, breaking his steel body in just seconds. This is called Chi wo Hau Zangeki (地を這う斬撃,Earth-Crawling Slash?) in Gigant Battle.
Mihawk slices the opponent with a spiral-like stream (very similar to Zoro's Sanjuroku Pound Ho) of compressed air with great speed. This, alongside with Mihawk's outstanding eyesight, makes one of the most speedy and accurate attacks shown in the whole series (to even strike a Luffy in Gear Second mode while he is moving in the middle of the war of Marineford).
In the anime and video games, the sword's blade is quite thick while in the manga, it is very thin. This may have been changed as of Episode 489 where the sword appears very thin like its manga counterpart. Also, the beads on the sword's hilt were initially red in the manga, while in the anime they are blue and green in color; in the manga the color was later changed to green. The background of the golden part of the sword is also green in color in the manga. A difference noticeable in the anime is that the blade of the sword emits purple when it is first used to Zoro (changed to green during the Marineford Arc) streaks when swung.