"Wonder Bebil-kun" is a surreal and darkly comedic anime series that revolves around the bizarre and often chaotic life of Bebil-kun, a young boy who is revealed to be the son of the Devil. The story begins with Bebil-kun being sent to live on Earth as part of a plan orchestrated by his father, who aims to conquer the human world. Bebil-kun is placed in the care of a human family, the Yamadas, who are unaware of his true nature. Despite his demonic origins, Bebil-kun initially appears to be an ordinary, albeit mischievous, child.

As the series progresses, Bebil-kun's demonic powers and sinister intentions become increasingly apparent. He frequently engages in acts of violence, manipulation, and destruction, often targeting those around him, including his adoptive family and classmates. His actions are driven by a desire to fulfill his father's mission of bringing chaos and despair to humanity. However, Bebil-kun's plans are frequently thwarted by his own incompetence, the resilience of the humans around him, and the interference of various supernatural entities.

The Yamada family, particularly the young daughter Mako, serves as a counterbalance to Bebil-kun's malevolence. Mako, who is kind-hearted and naive, often unwittingly foils Bebil-kun's schemes through her innocence and compassion. The dynamic between Bebil-kun and Mako is central to the series, highlighting the contrast between his demonic nature and her human goodness.

Throughout the series, Bebil-kun encounters a variety of otherworldly beings, including angels, demons, and other supernatural creatures, each with their own agendas. These encounters often lead to absurd and darkly humorous situations, further complicating Bebil-kun's mission. The narrative is episodic, with each episode presenting a new challenge or scheme for Bebil-kun to navigate, often ending in unexpected and chaotic outcomes.

The tone of "Wonder Bebil-kun" is a blend of dark humor, satire, and surrealism, with a focus on the absurdity of Bebil-kun's attempts to wreak havoc on humanity. The series explores themes of morality, the nature of evil, and the resilience of the human spirit, all while maintaining a sense of irreverence and unpredictability. The characters, particularly Bebil-kun and Mako, are central to the narrative, with their interactions driving much of the story's tension and humor. The series ultimately presents a unique and unconventional take on the battle between good and evil, set against the backdrop of everyday life.