Ryomen Sukuna, often simply referred to as Sukuna, is the primary antagonist in Jujutsu Kaisen and is known as the "King of Curses." In the series' lore, Sukuna was once a fearsome sorcerer who became an immensely powerful curse after his death. His power was so great that his body could not be fully destroyed, resulting in his remains being preserved as 20 indestructible fingers. These fingers now serve as cursed objects containing his malevolent energy.
When Yuji Itadori consumes one of Sukuna's fingers, Sukuna is resurrected, using Yuji's body as his host. Despite being trapped within Yuji, Sukuna possesses incredible strength, speed, and a vast array of cursed techniques. His personality is ruthless, sadistic, and cunning, often taking pleasure in battle and suffering.
Sukuna’s relationship with Yuji is complex, marked by an uneasy coexistence. He represents the darkest aspects of jujutsu sorcery, embodying an almost god-like presence among curses.