Haki, simply put, is a physical manifestation of will. It can be he will to survive a dire situation, save someone dear to you, or do something you want to do, the absence of even the slightest of doubt is necessary.
Thus, Haki is rightly said to bloom in battle.
The will to do something you want despite having someone standing in front of you, being able to break through this wall of waver makes Haki truly bloom.
The introduction of Haki levelled the playing field against the seemingly invincible logia type devil fruit users who can turn their entire body into the specific devil fruit power they possess.
It became one of the staple ways to measure how strong a character is and how they would fare in a fight.
Haki manifests itself in three different ways: The Colour of Observation, the Colour of Armament and the Colour of the Supreme King.
Let’s take a look:
1. Colour of Observation
Other names: Kenbunshoku no Haki, Perception Haki, Observation Haki
Notable Users: Charlotte Katakuri, Vinsmoke Sanji, Admiral Fujitora
Observation Haki allows the user to sense or ‘feel’ the life in something. The user can hear, see or even feel emotions of the target if their Observation Haki.
If advanced enough, the user can see just slightly into the future by sensing the other person’s will to do something. Charlotte Katakuri excelled in this and used it as his main weapon in combat.
Observation Haki, however, requires its user to be calm and composed in order to be used.
Observation Haki is an important weapon while dealing with an opponent that relies on invisibility techniques, as Fujitora uses his Observation Haki to circumvent his blindness.
The Mink tribe are speculated to specialize in a special kind of Observation Haki that makes them undetectable for other Observation Haki users.
This is seen repeatedly in the Zou Arc as Luffy failed to sense Pedro on top of the trees and all the various Minks hiding in the Whale forest.
2. Colour of Armament
Other names: Busoshoku no Haki, Armament Haki
Notable Users: Dracule Mihawk, Roronoa Zoro, Oden, Sword God Ryuma
Armament Haki allows its user to coat themselves in a layer of black coating that is harder than steel and is resistant to bullets, sword attacks and almost anything else that you can encounter.
If advanced enough it allows the user to destroy something from the inside. It also can be used to coat weapons to make them much stronger and effective.
Frequently coating your weapon with Armament Haki will result in the permanent blackening of the weapon, but it requires a humongous number of battles and coatings.
Armament Haki, depending on the strength, provides a complete defence against any offensive attacks such as swords and arrows. This can however be circumvented by using a higher level of Armament Haki.
Characters like Vergo and Pica were show to be able to coat their entire body in armament Haki, but they were both cut by Law and Zoro respectively.
Thus, it is speculated that the more area one covers in the coating of armament, the coating goes on thinning, and it is not advisable to do so.
3. Colour of the Supreme King
Other names: Haoshoku no Haki, Haki of the Supreme King, Conqueror’s Haki
Notable Users: Gol. D. Roger, Silvers Rayleigh, Monkey. D. Luffy, Whitebeard
Conqueror’s Haki has many unexplored abilities and potential to it yet. The most basic level of Conqueror’s Haki is able to intimidate or overwhelm an opponent.
A little further advanced is the ability to knock any opponent out by essentially forcing your will upon opponents with a weaker will.
Conqueror’s Haki is a very rare innate ability in the One Piece world and most of these people are either very successful pirates, leaders or at a high position in the Marines.
The mere possession of Conqueror’s Haki indicates the ability of the person to stand above others and lead them. Conqueror’s Haki can often be used to avoid having to fight fodder and knock out people who would just be collateral damage.
Characters like Luffy, Katakuri and Rayleigh are seen using this ability to knock people out so that they can fight in peace without involving anyone in the crossfire.