"Bottom Biting Bug" is a surreal and darkly comedic anime series that explores themes of existential dread, societal pressures, and the absurdity of human behavior. The story centers around a mysterious phenomenon where individuals are suddenly afflicted by an inexplicable compulsion to bite their own lower bodies. This bizarre condition, referred to as the "Bottom Biting Bug," spreads rapidly, causing widespread panic and confusion. The narrative follows a diverse cast of characters as they navigate the chaos and attempt to uncover the origins and meaning behind the affliction.

The protagonist, a disenchanted office worker named Hiroshi, becomes one of the first to experience the condition. His mundane life is upended as he grapples with the physical and psychological toll of the bug, which manifests as an uncontrollable urge to bite himself. Hiroshi's journey intertwines with that of a skeptical journalist, Aya, who investigates the phenomenon, and a reclusive scientist, Dr. Kuroda, who believes the bug may be a manifestation of deeper societal issues. As the condition spreads, the government imposes strict quarantine measures, leading to social unrest and moral dilemmas.

The series delves into the personal struggles of its characters, highlighting their vulnerabilities and the ways they cope with the absurdity of their situation. Hiroshi's relationship with his estranged family becomes a focal point, as does Aya's determination to expose the truth despite mounting obstacles. Dr. Kuroda's experiments reveal unsettling connections between the bug and collective human consciousness, suggesting that the affliction may be a metaphor for repressed desires and societal alienation.

Throughout the series, the tone oscillates between dark humor and poignant introspection, with the characters' interactions and decisions driving the narrative forward. The plot builds toward a climactic revelation about the true nature of the Bottom Biting Bug, challenging the characters—and the audience—to confront uncomfortable truths about human nature and the world they inhabit. The series concludes with an ambiguous yet thought-provoking resolution, leaving the ultimate meaning of the phenomenon open to interpretation.