The Black Flash is a powerful technique in the Jujutsu Kaisen universe that allows a sorcerer to momentarily exceed their normal cursed energy output and speed, granting them incredible destructive power and unmatched mobility. To use the Black Flash, a sorcerer must first accumulate a large amount of cursed energy within their body and then release it in a single, powerful burst. This can be done by either performing a series of consecutive cursed energy attacks or by using a special technique like the Cursed Speech.
When a sorcerer successfully executes a Black Flash, they will be enveloped in a black aura and their body will begin to glow with a blinding light. Their speed and power will increase dramatically, allowing them to overwhelm even the most powerful opponents. However, using the Black Flash is not without its risks. The immense strain on the body can cause severe injuries, and if the sorcerer is not careful, they could even die.