Emerging over a millennium ago in Japan's Heian Era, Ryomen Sukuna began as a human sorcerer. Historical jujutsu accounts detail his unprecedented power and merciless actions, including slaughtering elite forces like the Five Empty Generals and the Stars, Sun, and Moon Squads, earning him the title "King of Curses." Sorcerers eventually combined their efforts to defeat him, though they could not destroy him completely. His essence was sealed into twenty indestructible fingers persisting as special-grade cursed objects. Centuries later, in June 2018, high school student Yuji Itadori consumed one finger, becoming Sukuna's vessel and trapping the curse within his body. Sukuna later orchestrated a transfer into Megumi Fushiguro's body to gain greater freedom. He was born a twin to a starving mother; driven by primal instinct, he cannibalized his twin in the womb, an act foreshadowing his ruthless nature and contributing to his eventual resurgence. Sukuna's original form possesses four arms, four eyes, a large mouth on his abdomen, short pink-red hair, red eyes, and intricate black tattoos covering his body. These tattoos and a second pair of eyes beneath the host's natural eyes manifest on any vessel he controls. When inhabiting Yuji Itadori, his influence altered Yuji's appearance to include spiked pink hair pushed forward and the characteristic tattoos. After transferring to Megumi Fushiguro, he similarly modified Megumi's features, adding the tattoos and adjusting his hair to a spiked style. His innate domain, housing his consciousness, features a decaying shrine-like structure filled with bones and water, reflecting his destructive nature. Sukuna exhibits egotism, hedonism, and sadism, relishing chaos, destruction, and others' suffering. He openly delights in the prospect of massacring vulnerable populations. His philosophy adheres to social Darwinism, viewing strength as the sole justification for existence and dismissing weaker individuals. His extreme arrogance leads him to toy with opponents and prolong battles for amusement. Despite this, he displays high intelligence and strategic cunning, such as manipulating Yuji into a binding vow by tearing out his own heart to secure future control. He occasionally acknowledges formidable opponents like Jogo, whom he praised before killing, or Satoru Gojo, whom he commended posthumously, though these moments stem from a warped sense of honor, not genuine respect. He harbors particular disdain for Yuji Itadori, whose idealism and resistance challenge his worldview, provoking intense hatred. This animosity drove him to initiate a merger during the Culling Games purely out of spite toward Yuji. Sukuna's abilities establish him as the strongest sorcerer in history. He wields vast cursed energy reserves exceeding modern sorcerers like Yuta Okkotsu, with exceptional control allowing precise intensity adjustments. His primary offensive techniques are Dismantle, unleashing invisible slashes against inanimate objects or non-sorcerers, and Cleave, which adapts its power to an opponent's strength. He also commands the pyrokinetic Fire Arrow, capable of incinerating special-grade curses. His domain expansion, Malevolent Shrine, uniquely lacks a barrier; it manifests as a decaying shrine unleashing guaranteed-hit slashes within a 200-meter radius. He employs domain amplification to neutralize opposing cursed techniques, notably bypassing Satoru Gojo's Limitless. Mastery of reverse cursed technique enables rapid regeneration, such as regrowing limbs, and allows positive energy output to destroy cursed spirits. After possessing Megumi, he accessed the Ten Shadows Technique, summoning and controlling Mahoraga—a shikigami previously considered uncontrollable—adapting its power to counter Gojo's Unlimited Void. He strategically utilizes binding vows, such as restricting actions during Yuji's control for future autonomy, or enhancing his world-splitting dismantle after losing a hand. Beyond jujutsu, he is a master hand-to-hand combatant, effortlessly overpowering foes like Megumi, Jogo, and Mahoraga, with speed and reflexes enabling him to blitz opponents and evade attacks like Maximum Meteor. Sukuna's relationships are predominantly transactional or antagonistic. He maintains a longstanding association with Uraume, whom he encountered as a child due to their ice-based cursed technique; Uraume serves as his loyal subordinate handling practical matters. His dynamic with Yuji Itadori is marked by mutual loathing; Sukuna views Yuji as a temporary vessel and mocks his morality, while Yuji seeks eradication. This conflict intensifies when Sukuna exploits Yuji's vulnerability to possess Megumi, systematically breaking Megumi's spirit to maximize control. He shows fleeting interest in individuals with unique abilities, such as Megumi's Ten Shadows Technique, which he covets, or Mahito, whose idle transfiguration he resists effortlessly. He exhibits contempt for authority figures and conventional jujutsu structures. Across his appearances, Sukuna undergoes subtle development. Initially confined within Yuji, he engineers opportunities to seize control, culminating in the Shibuya Incident where he battles Jogo, decimates parts of Tokyo, and encounters Mahoraga. After transferring to Megumi, he engages in a prolonged showdown with Satoru Gojo, ultimately killing him using Mahoraga-adapted techniques and a binding vow-enhanced dismantle cut. During the Culling Games, he faces coordinated assaults from sorcerers including Yuji, Maki Zenin, and Kashimo, sustaining injuries that force him to reveal additional abilities like the lightning-based cursed tool Kamutoke. In a rare introspective moment following defeat, he confronts past resentments in an afterlife-like space, acknowledging his destructive path stemmed from unaddressed bitterness, though he reverts to his nihilistic outlook upon reincarnating. His actions consistently drive much of the series' conflict.