Ittou Rasetsu

"Vision, taste, hearing, touch, smell―right now he didn't need any of them. In this instant, he didn't even need to breathe. Abandoning all of those things, he concentrated the strength left over. All of his flesh. All of his brain. All of his blood. All of his cells, everything from them. His personal vitality, stamina, magic power, potential, he mustered all that he had― And for an instant, he broke past his limits!!!"

- Tne narration describing Ittou Rasetsu.

Ittou Rasetsu is the Strongest Noble Art of Ikki Kurogane and also an improved version of his Ittou Shura.

Description
Ittou Rasetsu is an improvised version of Ittou Shura, in which Ikki had shut down all his five senses along with all his body's function such as being able to breathe as well as mustering all the strength that he had within himself for a single second instead of the usual single minute, which makes him ten times stronger, it instead strengthens himself almost over a hundred-fold for a single swing.

At first, unnamed, it was given the name Ittou Rasetsu by the three spectators for his match against Touka Toudou. It was described as being a technique exceeding the limits beyond limits and it won't be a man who fell into the realm of Shura, but the Rakshasa, which exceeded humanity.

After Ikki reached Awakening during his match against Stella in the finals of the Seven Stars Sword Art Festival, his magic power had increased so that he could use Ittou Rasetsu right after Ittou Shura.

In the Vermillion Empire Arc, training with Edelweiss, Ikki was able to improve his magic control, able to retain the immense powers of Ittou Rasetsu inside of himself, concentrate the strengthening of this self-destructive noble art on the required parts instead and pouring all of the wasteful power that would've ended up damaging himself inside of Intetsu instead. Unlike when he used Ittou Rasetsu before, Ikki didn't receive the severe injuries as before and still had enough strength to fight, but he still drained his magic.

Weaknesses
Despite being ten times as strong as Ittou Shura, Ittou Rasetsu put a heavier strain on him than the original more than his well-trained body was able to endure causing several injuries the first time used as such it is considered to be a self-destructive Noble Art used as a last resort.

However, Ikki was able to overcome all the severe self-destructive drawbacks of Ittou Rasetsu after training with Edelweiss to improve his magic control, letting him continue fighting after using it albeit draining his strength and magic. He regained most of his strength through autophagy, but he would be able to fight for at five minutes.

Trivia

 * Ittou Rasetsu is a reference to an alternative name for the Rakshasa, a demonic being found in Hinduism and Buddhism known for their bestial ferocious nature and cannibalism, which is also interchangeable in-between Shura or being another form of one.
 * Ikki could be seen as becoming similar to a Rasetsu in cannibalizing all his strengths for just a single move, which allowed him to surpass humankind in an instant.