Black Flash

Black Flash (黒閃) is a special kind of Jujutsu attack that greatly amplifies the user's physical hit when the Sorcerer applies their Cursed Energy within one millionth of a second.

Description
Black Flash is a distortion in space that occurs Cursed Energy is applied with 0.00001 seconds of a physical hit. When a Sorcerer is able to achieve this, their Cursed Energy flashes black, and the power of their strike is multiplied two and a half fold.

This technique requires incredible concentration and no Jujutsu Sorcerer is capable of using it at will, not even Satoru Gojo. Sorcerers who managed to unleash Black Flash have an immeasurably higher understanding of the essence of Curse Energy. For Sorcerers, the mental process of manipulating Cursed Energy becomes as simple as breathing.

Kento Nanami
Nanami believes that using Black Flash consecutive times isn't anything to celebrate. After using the technique more than once, doing so repeatedly is not as difficult as initially releasing Black Flash. Nanami compares using Black Flash to being in a zone of focus similar to what professional athletes experience while in a game, feeling as if they're the center of everything. Nanami's record was four consecutive uses of Black Flash, and he claims he got lucky.

Yuji Itadori
During the Goodwill Event, Aoi Todo was able to teach Yuji to harness his Cursed Energy by combining it with his superhuman speed and strength. By explaining how to make Cursed Energy flow properly and pitting Yuji against Hanami, Aoi was able to help Yuji unleash the ability. The attack was able to do great damage to Hanami just from one strike. By landing multiple Black Flash attacks while fighting alongside Aoi, Yuji was able to overwhelm the Special Grade Curse.