How does Haki work?

Question

Haki seems to not only affect the Devil Fruit user, but also all the other weak enemies. What is the mystery behind it? It seems like willpower but there are so many different types. I have read through One Piece Wiki but I still haven't got a clear picture.

Haki is a power that lies dormant in all the world's creatures... "Presence", "fighting spirit" and "intimidation"... It is not different from the things that humans can naturally sense such as these... 'The act of not doubting'. That is strength!

^{— Silvers Rayleigh explaining Haki to Luffy at the start of his training}

Answer 1

What we know is that Haki is a manifestation of inner strength/willpower/spirit. It is similar to chakra/ki/Nen. It has not been shown or implied to be usable in any way besides the three know types. It is a latent ability in sentient beings (and that we know of only sentient beings) that exists in the world of One Piece. I do not mean spirit as another word for ghost but instead soul/essence/life energy/determination.

There is no implicit mystery behind it or rather I did not pick up on hints that there is a secret. It is a physical/spiritual law of that universe that does not really exist in this one.

The reason it works on logia users seems to be that hitting with one's spirit will hit their spirit. Even if their body has been turned to flame by their logia, hitting their spirit will still do damage and turn their body back it normal. Any more explanation of this would require an explanation of the nature of a devil fruit (which I don't fully know but Oda and Vegapunk do).

Some fans have been speculating as to whether Haki without understanding Haki is the cause of some of the more outstanding displays of ability in the early series but this is not confirmed. This includes Pell's survival, cutting steel, anything Oda calls "heart" etc. That is the only thing I know of that can be considered an outstanding mystery.

There are three types of Haki and they can be read on said wiki:

1. Observation Haki/Mantra allows the user to detect the spirit of other people. It allows him to detect where they are and predict any attack they are about the throw.
2. Armament Haki which hardens a weapon/skin/clothing of the user at will to protect against blows. This allows the user to hit with his spirit and hurt logia users that are immune to normal blows with their fluid state.
3. Conqueror's Haki allows the user to force his will at a distance towards others. This can induce terror in the recipient or cause them to pass out. Often this is used to convince beasts to flee or follow the orders of the user. Apparently it can also be used to push away inanimate objects as was done by Shanks on Whitebeard's ship.

In essence Haki is always the same energy. The powers are to sense it in others, focus and use it in oneself, or push it out of oneself at others.

Answer 2

Haki is indeed difficult to get your head around but you get more detail about Haki when you get more into the series and then you even find out about the Advanced version of the 3 types of Haki I am not sure if you want to know about just basic Haki or Advanced but seeming as the basics of it has already been explained I can explain how Advanced Haki works. Starting of with the Colours of Observation or Observation Haki it can do the same as basic Observation Haki but on a whole other level if trained enough you see around 10 to 20 seconds into the future you could probably train it even more to see into the future not proven yet though so it is really broken. Next Colours of Armament or Armament Haki it has the same effects on devil fruits like basic Armament Haki but with basic Armament Haki it is pretty destructive but with Advanced Armament Haki when you punch an object the blow comes from the inside so it is destroying things from the inside out and also proven by Luffy you don't even need to touch the object or person to actually hit them so basically someone can dodge your attack barely but they will still be hit from the inside out I haven't looked that much into the Advanced version of Armament Haki but I heard that it is basically pouring your Haki into the object or person and that is what attacks them from the inside I actually don't know if this is true I just heard that's how it works. Finally we have The Supreme King or Conquerors Haki the Advanced version allows you to imbue Conquerors Haki into your weapon or fist/arm basically like Armament but with Conquerors you can use the clash between Gol D. Roger and Whitebeard for this as an example again like Armament don't know too much about Conquerors Haki but that is how it works and what I know of it now Luffy can also use this form of Haki as well so you see him use it and that is about it for the 3 types of Advanced Haki pretty confusing for the last two since they have only been shown recently so we will just probably have to wait after Wano to get a better understanding of it.