The Evil Eye is a powerful yokai spirit from the manga and anime series DAN DA DAN, originally introduced as a primary antagonist who later transitions into a complex supporting role. His existence is rooted in profound tragedy, having once been a young boy during the Edo period who was chosen by the Kito family as a human sacrifice. The Kito family had a long-standing practice of sacrificing people to a monstrous entity known as the Tsuchinoko, a giant worm, in order to keep a nearby volcano dormant and protect their village. The boy was kept in solitary confinement, starved, and eventually burned alive. Before his death, his only wish was to be able to play with the other children he could see from his prison.

After his physical death, the boy did not immediately become a malevolent spirit. For a time, he remained a playful ghost. However, his transformation into the vengeful entity known as the Evil Eye occurred when another child was imprisoned in the same house to be sacrificed. The spirit desperately tried to save the new victim but failed because he had no physical form. Witnessing another child suffer the same cruel fate broke his spirit, and his compassion curdled into an intense, burning hatred for all of humanity. He swore vengeance on the Kito family, and over centuries, that hatred expanded to encompass every human being.

The Evil Eye is characterized by a terrifying and aggressive personality, driven by a singular desire to kill all the humans he encounters. He is sadistic, enjoys combat, and shows no mercy towards his opponents, displaying a particular disdain for those who flee from a fight. Despite this monstrous exterior, the core of his motivation is revealed to be a tragic and childlike misunderstanding. His long-deferred wish to play became so twisted by his suffering that he came to equate the act of killing humans with playing with them. He is, in essence, an extremely powerful being who has no real conception of right and wrong, lashing out with the raw, unfiltered rage of a child who was horrifically wronged.

In the story, the Evil Eye is bound to the cursed house where Jiji Enjoji, a childhood friend of the protagonist Momo Ayase, lives with his parents. The yokai is drawn to Jiji because of his exceptionally high levels of both spiritual energy and natural athleticism, seeing him as the perfect vessel. After Jiji sees the Evil Eye's tragic backstory and is moved by pity, he makes a desperate promise to let the spirit possess his body so they can be friends and play together. This act of kindness backfires catastrophically, as the Evil Eye takes full control, transforming Jiji into a nearly unstoppable force. This possession marks the Evil Eye's central role as the primary antagonist of the Cursed House Arc. However, Okarun, who has been empowered by the Turbo Granny yokai, engages the possessed Jiji in a fierce battle. After a hard-fought fight, Okarun realizes the Evil Eye's true nature is that of a child who just wants to have fun. He negotiates a deal: the Evil Eye can fight Okarun once a week, every Tuesday, but in exchange, he is forbidden from killing any other humans. This pact successfully manages the threat and begins the process of integrating the Evil Eye into the main group.

The Evil Eye's key relationships are central to his development. His connection with Jiji is unique, as Jiji willingly offered his body as a host. While the Evil Eye often takes control, there is a symbiotic coexistence, with Jiji sometimes able to suppress the possession, such as when exposed to hot water. The most crucial relationship is with Okarun. The Evil Eye respects Okarun as a worthy rival and sees their scheduled fights as a game, which provides an outlet for his violent impulses. Over time, he develops a grudging tolerance for the other members of the group, including Momo, Turbo Granny, and even Seiko Ayase. His developmental arc sees him evolving from a pure, mindless avatar of vengeance into a dangerous but controllable ally who, while still a threat, is now part of the status quo, occasionally even protecting his found family.

The Evil Eye possesses a range of devastating supernatural abilities. His most iconic power is his malevolent gaze, a psychic wave that compels anyone who makes direct eye contact with him to attempt suicide. This ability is potent enough to cancel out similar psychic waves emitted by the Tsuchinoko worm. As a yokai, he has the power of possession, taking over the body of his chosen vessel to act in the physical world. He can also share his traumatic memories with others through eye contact, a method he used to lure Jiji into their pact. In combat, he exhibits immense physical strength, speed, and durability. His primary offensive and defensive techniques involve summoning the physical manifestation of the grudges of all the previous sacrifices. He can compress these grudges into a dense, destructive ball that he kicks with incredible force, called a Grudge Ball. For defense, he can shape the same grudges into an impenetrable, house-shaped dome known as the Grudge House, which isolates him from the outside world and protects him from attacks. Later in the series, when Jiji learns to harness his own ki, he can synchronize it with the Evil Eye's power to create even more advanced techniques, such as firing energy blasts. Despite his power, the Evil Eye has notable limitations, such as his childlike and impulsive nature, which makes him vulnerable to manipulation and negotiation, as well as the strange weakness of being re-submerged within Jiji upon contact with hot water.