Ittou Rasetsu

"His personal vitality, stamina, magic power, potential, he mustered all that he had. And for an instant, he broke past his limits!!!"

Ittou Rasetsu (一刀羅刹, One-Blade Rasetsu) is the Noble Art of Ikki Kurogane and 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 bodies' 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 making it ten-times as powerful further increasing his strength hundred-fold.

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.

During the Vermillion Empire Arc, Ikki trained with Edelweiss on top of a snowy mountain top to improve his magic control by balancing on a pointed tip for hours. Afterward, he was able to concentrate the strengthening granted to him on only the necessary parts instead of focusing on his while body and pouring the wasteful energy that would've ended up damaging him into his Intetsu instead. Unlike when he used Ittou Rasetsu before, Ikki didn't receive the same severe injuries as before and still had enough strength to fight.

Weakness
Despite being ten times as strong as Ittou Shura, Ittou Rasetsu puts an even heavier strain on him than the original more than his well-trained body is capable of enduring and causing several injuries the first time it was used and as such as considered a self-destructive Noble Art used as a last resort.

Ikki was able to overcome the severe drawbacks of using Ittou Rasetsu after training with Edelweiss in order to improve his magic control, letting him continue fighting after using it albeit it was through using autophagy, but he would be able to fight for at least five minutes.