Ittou Shura

"One minute was enough. It was fine to ignore what happened afterward, but for one minute he'd become strong enough to beat anyone." Ittou Shura (lit. Blade of Shura) is the Noble Art of Ikki Kurogane.

Description
Ittou Shura is a Noble Art form of Ikki's that forcefully removes all of Ikki's physical limits, allowing him to gain tremendous power while ignoring survival instincts of the human body. This technique, although grand, is only able to be maintained for a minute. The technique does have major drawbacks, most notably its usage limit of once per day, due to the incredible amount of stress it places on Ikki's body. He has been seen several times in the hospital after using this technique. Opponents have used the "once-a-day" limit against him before in order to cripple his chances of victory.

During his match against Tohka Todo, Ikki uses an improved version of the Ittou Shura, Ittou Rasetsu, to defeat his opponent.

Weakness
Ittou Shura drains the entirety of Ikki's stamina, in one minute, so he will become unable to fight, for an extended amount of time.

After reaching his "Awakening" Ikki's magic power increased, so that he could even use Ittou Rasetsu after Ittou Shura. This only happened once, as Ikki is still unable to control his abilities.

Trivia

 * The Shishou martial arts technique, Kirinkou, is very similar to Ittou Shura.