What skills introduced prior to the formal introduction of Haki are Busoshoku Haki based?

Question

There are 6 techniques that are the keys to Rokushiki. Despite a claim in another answer from a well informed user that none of the CP9 members are haki users, several of these techniques seem to be rudimentary forms of Busoshoku Haki. It seems completely reasonable that the marines would be training them in the use of Haki based skills.

In particular: Tekkai, Rokuogan, and Shigan seem to clearly be Haki based. There are, however, some points against this including Luffy's reaction to Shigan.

Geppo and Rankyaku could feasibly be viewed as imparting ones willpower/Haki to the air like a projectile.

Only Soru does not seem to fit this but Sanji's simular technique (Blue Walk) was (at least partially) transfered to Nami when his mind was transfered. By this answer Haki is transferred but not physical strength.

There are several other techniques that, if these are Haki based, would also need to be Haki based such as Sanji's Sky and Blue walks and Zorro's ranged sword attacks.

Finally we address swordsmen. Not covered by the CP9's skill but still seems to be early stages of learning Haki is Zorro's cutting of steel. His sword would normally not be able to cut something as hard or harder than itself but he learns to impart his willpower to it to make it cut what and only what he wants it to. This is complemented by an early use of observation haki immediately prior to it in his fight against Mr. 1.

My one question is therefore: Are there any abilities that were shown prior to the introduction of haki on the show (such as the potential examples above) that have either been shown to work by using Busoshoku Haki (knowingly or not) after it's introduction or have been confirmed by canon sources to be Haki?

As I consider it Haki was introduced on Amazon Lily and in the several instances that were observed on the archipelago. The nature of this question invites speculation as I've done above but I would prefer justification in canon. I understand anime physics don't have to be realistic but this would explain alot.

Answer 1

I will first use your examples to explain Rokushiki and Haki and then give a comparative conclusion using the wiki.

Rokushiki

Rokushiki was mainly explained in chapter 348 and was explained to be pure body strength with every technique. Rob Lucci confirms this after the CP9 had defeated the Strawhats for the first time.

• Tekkai

  Our bodies are trained to the point of mimicking an iron shell.

• Soru

  It only seems as though I've disappeared. With the explosive power of my legs...

• Geppo (See also this question

  (Also with the explosive power of my legs) I can kick the air and float...

• Rankyaku

  Nami: They cut the wall with their kicks!?
  Kalifa: If you have the speed to create a kamakaze, then it's possible...
  

• Overall

  We've trained our bodies to great extremes since we were young.

Strawhat crew's attacks

• Sanji's sky and blue walk are basically like Geppo. The more power you gain in your legs, the faster you can move. So if you master this technique anyone could do it, as we have seen Sanji do in Nami's body. This could be argued to only have been possible by Sanji somehow imbuing Haki into Nami's legs as she would not have been as powerful to use blue walk. That's why I mentioned that technique is needed also. After being a thief and being on the run for most of her teen years, Nami has the physical potential of using blue and maybe even sky walk, she just didn't learn the technique needed to do so.

• Zoro's ranged attacks are basically like Rankyaku. The more speed you can put in your slashes, the bigger the slash gets. Haki can be imbued to make the slash stronger as Law did against Vergo or when Mihawk slashed at Whitebeard (the fact whether Haki was imbued here, is debatable though). Haki can be imbued, but it isn't needed to create ranged slashes as explained with Rankyaku. Mere arm power or slash techniques would be enough.

• Zoro cutting steel aka Mr.1
  As explained in the following question, Zoro did not use haki in Alabasta

Haki

Haki on the other hand is a pure mental power and it might not even be possible to get it out even with enormous training.

• Overall

  Haki is a power that lies dormant in all the world's creatures, but a majority of humans go without noticing this power or perhaps finish their lives failing to ever pull it out, even if they try...
  

• Kenbunshoku Haki

  The ability to sense the opponent's presence even more strongly is haki with the color of observation.
  

• Busoshoku Haki

  This power can also be imbued into weapons (and can thus not be a mere physical trait as you can't train weapons)
  

• Haoshoku Haki

  This color of the conquerer however, cannot be trained and strengthened, even if you are able to control it.
  

Difference

Therefore to conclude, Rokushiki is not Haki. The result might be similar, but they are fundamentally different. Rokushiki is based on pure physical power, while Haki is based on will power. You could therefore technically have both Rokushiki Tekkai enhancement and Busoshuoku Haki at the same time, although this has not been shown in the series thus far. This is also why Rokushiki can be easily taught by becoming physically stronger, while Haki must be developed by becoming mentally stronger, which isn't as easy to do. Rokushiki will therefore not make the user able to negate Devil Fruit powers and hit Logia users for example.

Tekkai is similar to Busoshoku Haki, as both reinforce the users body in some way, the difference being that Haki is based on the user's willpower and Tekkai is based on the user's physical power. Also, Tekkai is more inclined to defense and the user exhibits no movement while it is active. In comparison, Busoshoku Haki is capable of both offense and defense.

Source on Tekkai

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Other information

If you want to read more about Haki, see the question about the abilities that are transferred when hearts are interchanged between bodies
If you want to read more about Geppo, see the question about how CP9 members and Sanji can run in the air

Usage

Background

It was used by Garp for the first time against Luffy to bypass his Devil Fruit power and hurt him in Water 7. Later, Sentomaru used a Haki-imbued attack against Luffy, which made the Straw Hats think he was a Devil Fruit user due to their lack of knowledge about the ability. Afterwards, Rayleigh used Haki to stop Kizaru and even touch his Logia body. The first time the Kujas named this ability "Haki", they were shown wielding Haki-imbued arrows. During the Marineford War, Haki was also used many times by marines and pirates alike. It was shown that Haki is very common in the New World, unlike in Paradise where Haki users are fairly rare and almost nobody knows about it. It is later explained by Rayleigh once he begins training Luffy.

Examples

• It can be used to augment the user's own attacks, projected ahead of the user as pure brute force, or imbued in weapons to increase their effectiveness. Any attack enhanced by Busoshoku Haki hits immensely harder than it would normally be without it. The Kuja's Haki-imbued arrows, for example, are capable of penetrating solid stone.
• This type of Haki also has the ability to bypass the powers of a Devil Fruit user, touching the "substantial body" beneath whatever protection the fruit provides, such as the case of body-altering Devil Fruits such as Logia or Paramecia users. However, unlike Kairoseki, it does not negate a user's Devil Fruit powers, allowing them to defend themselves, and continue fighting normally. By the same effect, this Haki can also be used as a higher level of offensive, more so than just bypassing a foe's Devil Fruit powers.
• A heavy concentration (or coating) of this Haki can be used to harden parts of one's body, turning the area black, thus making the user denser and more formidable, and giving their attacks greater power. Although Luffy, the first in the mainstream storyline to demonstrate this effect, named the technique as Busoshoku: Koka (武装色 硬化 Busō-shoku: Kōka?, Color of Armaments: Hardening), no other users except Donquixote Doflamingo, such as Vergo and Smoker referred to this method by such a name.
• Busoshoku Haki works independently of the user's Devil Fruit, as shown when Luffy uses it to enhance his Gear Third attack underwater. This type of Haki may not be equipped to attacks that are not from one's body except for weapons, or anything generated from one's own body (like Kizaru's laser beams, Marco's flames or any other energy/non-solid attacks based on Devil Fruits). So, those who attack with parts of their body can combine their Haki and Devil Fruit powers.

Source on Busoshoku Haki