Grübchen, often referred to as Ekubo, which translates to dimple, is a significant character whose role evolves considerably throughout the series. He is initially introduced as an upper-class evil spirit, or a powerful ghost, with a deceptive and ambitious nature. His spiritual form is typically depicted as a small, green, disembodied face with prominent red circles on his cheeks, a feature that gives him his nickname. Despite his comical appearance, he is frequently described by other characters as having a very foul smell and being generally disgusting and unsettling.

In his background, Grübchen was once a spirit with grand aspirations to become a god. To achieve this goal, he possessed a human and established a massive, happiness-themed cult known as "LOL" to gather followers and worship, thereby boosting his own power. His plan was ultimately foiled when he encountered Shigeo "Mob" Kageyama, who defeated him and stripped him of the majority of his spiritual capabilities. After this defeat, Grübchen begins to follow Mob, ostensibly with the stated intention of waiting for a moment of weakness to take over his powerful body. He declares himself Mob's self-proclaimed spiritual adviser, a role that serves as a cover for his true opportunistic motives.

Grübchen's personality is a complex mix of cunning, selfishness, and pragmatism. He is an opportunist who is willing to do almost anything to increase his power, yet he possesses a sharp intellect and a deep understanding of how other people's emotions and weaknesses function. Unlike many antagonistic spirits, he is not driven by mindless rage or pure malice; instead, he is calculating and manipulative, often using hypnosis or psychological influence to achieve his ends. Despite his evil spirit classification, he develops a grudging respect and a genuine, albeit complicated, bond with Mob.

His role in the story is primarily that of a foil and a reluctant ally to the protagonist. He begins as an antagonist but quickly transitions into a member of the "Spirits and Such" consultation office, acting as a source of cynical commentary and spiritual expertise that Mob and the fraudulent medium Reigen often lack. Grübchen serves as a narrative tool to explore themes of power, ambition, and personal growth. Unlike the human characters who struggle with social and emotional connections, Grübchen's journey is about his shifting identity from a simple, power-hungry ghost to a being capable of loyalty and self-sacrifice.

His key relationships are central to his development. His bond with Mob is the most important, as he moves from viewing Mob as a vessel to steal to seeing him as a person he genuinely cares for and wants to protect. This relationship is a slow burn; Mob's unwavering sincerity and kindness gradually chip away at Grübchen's cynical and selfish exterior. He also interacts frequently with Arataka Reigen, and while the two often bicker and compete for influence over Mob, they share a common goal in looking after the boy's well-being. Grübchen also plays a pivotal role as a temporary mentor to Mob's younger brother, Ritsu, helping him hone his newly awakened psychic powers for his own ulterior motives, though this alliance is fraught with manipulation.

Grübchen's development is one of the most compelling arcs in the series. He starts as a classic villain who wants to dominate humanity. After his defeat and subjugation, he remains morally ambiguous, frequently suggesting pragmatic but ruthless solutions to problems. Over time, his exposure to Mob's philosophy of kindness and self-improvement causes a genuine internal shift. In the third season, this evolution reaches its peak as he fully embraces his role as Mob's protector, culminating in actions that are entirely selfless, a stark contrast to his original personality. His journey illustrates that even a being made of negative emotions can find purpose and redemption through a meaningful connection.

As a spirit, Grübchen possesses several notable abilities. His primary power is possession; he can enter and control the bodies of living beings and inanimate objects. When possessing a human, he can unleash the full physical and spiritual potential of that body, making the host far more powerful than they would normally be. However, he cannot fully control a powerful psychic unless they give him explicit permission. He is also a master of hypnosis, capable of influencing the minds of large groups of people to create mass hysteria, loyalty, or forgetfulness, a skill he famously used to build his cult. After his initial defeat, his raw power is significantly diminished, forcing him to rely more on his cunning and psychological manipulation rather than brute force. Despite this reduction in strength, his experience and knowledge of the spiritual world make him an invaluable, if unpredictable, ally.