1. “I will sink you with this, the strongest Black Blade”- Mihawk at Baratie talking about Yoru
2. “My swords are heavier”- Zoro at Arlong Park talking about Wado Ichimonji and random swords
3. ”It’s cursed isn’t it?”- Zoro at Loguetown talking about Sandai Kitetsu
4. “This One is a problem child”- Zoro at Whiskey Peak talking about Sandai Kitetsu
5. “I give you this black blade, Shusui”- Ryuma at Thriller Bark
6. “This Sword is heavier than the rest… it has a temper”- Zoro at Thriller Bark
7. “Forgive me Red hair… My blade knows no restraint”- Mihawk at Marineford
Given that we’ve learned that Blades are made black after a long period of time battling and this is somehow a feat worthy of praise, I would like to recontextualize a lot of these lines from before to especially give a new understanding to Mihawk’s last line there.
Theory 1. Black Blades and Cursed Blades
The first theory is gonna separate these two. Black Blades are a sign of prestige and proficiency in Swordsmanship as Gyukimaru in Wano says Shusui being a black blade makes Zoro unworthy of wielding it.
Cursed swords on the other hand cause wanton destruction and this isn’t a good thing as emphasized with Koshiro’s teachings to Zoro about the mark of a good Swordsman being the ability to only cut what they want to cut which Sandai Kitetsu tries to prevent.
Therefore Black blades=Good, Cursed blades = bad
Theory 2. Heaviness
As seen from dialogue 2, most would infer that Zoro means heaviness in a metaphoric sense regarding Zoro having bigger dreams and ambitions resting on his swords than the likes of Hachi at the time. And I believe that’s true. Someone’s dreams/will to achieve their dreams do in fact cause the swords to be “heavier” but I don’t think it stays purely a metaphor as the will increases to exponential capacities since we know at some point will does manifest as Haki.
We know that when someone uses Haki to make themselves strong or sturdier, they aren’t actually gaining mass so in the same way, swords don’t get heavier physically when someone puts Haki on them. Consequently when Zoro says Shusui is “heavier” he means it the same way he also called his own swords “heavier”, Zoro could literally feel the Will of Ryuma from the sword and it made the sword “heavy”.
Therefore, Zoro could feel his swords and Shusui are heavy because of the will behind them.
Theory 3. Cursedness
As established above regarding cursed swords being the antithesis of Black Blades as far as good Swordsman practice, Cursedness must be born from the antithesis of Will in Sword practice. This will in sword practice being the ability to cut only what you want to and not wanton destruction.
The cursed swords are said to be associated with people who end up dying horrifically and I believe this is because the swords were used by people with severe blood lust who got into so much careless killing that their swords were permanently imprinted with a twisted carelessness that persisted into the people who wield them afterwards.
Theory 4. Problem children, Tempers and No restraint
It’s now clear how the personalities of the swords are born, One being a child who can’t control themselves(cursed sword Sandai Kitetsu) and the other being a strong willed person with a temper of their own(black blade Shusui)
Yoru on the other hand seems strange, for the sword to have “No restraint” like a cursed sword but to then also be a black blade.
Theory 5. “Forgive me Red hair…”
I believe this line in question by Mihawk has extra context because it was after an apology to Shanks, as though he knows this is almost out of his hand now that he’s drawn his sword. But Mihawk wouldn’t be a good Swordsman if he couldn’t control what he wanted to cut and his sword definitely wouldn’t have been turned black to begin with, it would’ve become a cursed sword.
The reason for this contradiction is because the Mihawk of Marineford isn’t the same as the one who turned his sword black. Mihawk changed drastically sometime after his sword became black to the point that he no longer shares the same mindset as his sword now and is actually apologizing for his actions.
The Mihawk who made his sword black was a battle monger who lived for a dream to become the best and as he strives for the best, he made sure to literally go all out every single time and essentially crush his opponents but he still maintained proper sword practice that he wasn’t cutting just anyone, he just never went easy on anyone after deciding to cut them. As such, his sword was stained Black with the will to go all out at every turn with no restraint, especially with his legendary duels with Shanks. But of course, Shanks decided to severely change his ambitions by passing his will to Luffy and Mihawk lost what had become his only rival on the planet and Mihawk slowly and gradually fell into a depression to the point now that he can’t even recognize who he previously was, with his own sword basically having a separate personality from him now.
Therefore Mihawk apologizes and basically blames his sword for his own actions of trying to kill a person he knows Shanks likes because at this point his sword is a reminder of a different person he used to be and can barely recognize since he, like Zoro, can still feel that other will in Yoru and he just can’t relate to it anymore even though it was previously his own.
*Theory by ImmaIvanoM
