When a fighter pulls out their spirit to it's fullest, they are able to manifest it on the material plane. To exert one's dominance over reality itself, to take one's aura and give it material form. That is the highest level of Bushokoku haki! It is what you've been unconsciously doing when you draw out your "Asura".
However, as you did it unconsciously you were only able to pull it out at times of great desperation, when you're at your wits end and you have been pushed to the brink. However with practice, you would be able to draw out this power whenever you so desire. This shall be the next step in your training.
....
"I must admit that I'm impressed. You mastered this much faster than I expected. Perhaps it's time we looked at a limiter."
"A Limiter?"
"Raising the strength of one's spirit is not an easy feat. Only as the user itself grows stronger does their spirit grow more powerful. However, if you were to limit the amount of spirit you wielded at any given moment, you would force your spirit to develop even faster, and whenever you did decide to unlock it you would be in possession of even greater power."
The Hawk eyed man approached me, and before I could react, he had slashed through my left eye with his kogatana.
"Keep that left eye closed, and only when you are ready to unleash the full strength of your spirit do you open it."
I looked around us, we were in a pretty tight spot. To our left was the Yonkou Big Mom and her officers, to our right, the Yonkou Kaido and his officers. In front of us was Orochi and the remnants of his army. Things weren't looking favourable at all. All that was left, was a single path of retreat. It would take a miracle for us to escape. It's a good thing that's exactly what I had in mind.
"20 minutes".
Law turned to look at me.
"Huh?"
"I should have enough haki for 20 minutes. Take those you can save and retreat, for the next 20 minutes, I would not allow any of them to leave this island. Besides, I can't really guarantee the safety of my allies when I do this. That goes for you to Shitty Cook. Help our forces retreat."
The first form, no the second, I opened my left eye and unleashed the seal on my spirit. The grass at my feet shrivelled up and withered instantly, and the wailing of a thousand banshees could be heard.
"Demon spirit incarnation: Susanoo."