Ekubo is a high-ranking evil spirit who serves as a major character in the narrative. His true origins and any details about his life before becoming a spirit are completely unknown. He is easily recognized by his appearance, which initially manifests as a large, muscular, and intimidating spectral form with distinctive red, human-like markings on his face. After being defeated in his first encounter with the protagonist, he loses most of his power and is reduced to a small, floating, green, balloon-like shape sometimes described as a "talking ugly jellyfish". In this weakened state, he can still manifest arms and legs at will and can choose to be visible only to other psychics or to everyone.

Personality-wise, Ekubo is driven by a grand and selfish ambition: to become a god worshipped by all of humanity. He is articulate, confident, often referring to himself in a grandiose manner, and initially appears cold, calculating, and willing to manipulate anyone, including middle school children, to achieve his goals. He founded a religious group called LOL to gather followers and study human psychology for his own ascension. Despite his egoism, he is not purely villainous. He prefers peaceful and non-violent methods of control, considering it incompetent to damage the bodies he possesses.

Ekubo's primary role in the story begins as an antagonist and potential threat, but after his crushing defeat, he becomes a constant, if initially unwelcome, companion to the protagonist. He pretends to be helpful, offering advice and protection, with the secret motive of gaining trust and eventually exploiting the protagonist's immense power. Over time, this calculated relationship evolves into something genuine. He demonstrates a sense of responsibility, such as when he helps rescue the protagonist's brother, and shows true loyalty, even risking his spiritual existence to save the protagonist from a trap. His most significant relationship is with the protagonist, transforming from manipulator to a peculiar ally, a secondary mentor, and ultimately, a true friend. He also becomes an occasional, grudgingly accepted ally to other central characters, who eventually acknowledge his presence as part of the team.

Ekubo undergoes significant development, culminating in a major conflict where he finally puts his godhood plan into action. By absorbing the power of a divine tree, he regains his powerful, muscular form and gains even greater, golden, godlike abilities, allowing him to brainwash people on a national scale. However, his confrontation with the protagonist makes him realize that his true, deepest desire was not power, but friendship and belonging. Reconciling, he abandons his dream and sacrifices himself to save the protagonist from a rampaging spiritual force, exhausting all his power and vanishing. He is later able to return due to the protagonist's own uncontrolled powers, and in the end, he remains a faithful companion.

As an upper-class spirit, Ekubo possesses a variety of notable abilities. Even after being weakened, he can possess ordinary humans, bringing out their latent physical potential to superhuman levels, with his signature red cheek marks appearing on the host. He can also use hypnosis to manipulate crowds and has basic telekinesis. In his original, more powerful state, he could transform his body, regenerate damage, and fire a devastating energy laser called the Wraither Beam from his mouth. In his ultimate God form, his power is amplified to a devastating degree, granting him incredible strength, speed, barriers, and the immensely powerful God Beam.