"Kyōran Kazoku Nikki" centers around a peculiar family assembled by the enigmatic Chairman, who tasks them with creating a "normal family" as part of a mysterious experiment. The protagonist, Kyouka Midarezaki, is a young girl who becomes the family's "daughter" after being rescued from a life of hardship. The family consists of bizarre and eccentric members, each with unique abilities and backgrounds. Ouka Midarezaki, the self-proclaimed "father," is a powerful and flamboyant individual with a penchant for theatrics. Yuka Midarezaki, the "mother," is a calm and nurturing figure with a hidden, more dangerous side. Ginka and Senka, the "sisters," are genetically engineered beings with superhuman abilities, while Shionji, the "brother," is a quiet and mysterious boy with a tragic past.

The narrative unfolds as the family attempts to navigate their daily lives while adhering to the Chairman's directives. Their interactions are often chaotic and comedic, driven by their conflicting personalities and the absurdity of their situation. However, beneath the surface lies a darker undercurrent, as the family's origins and the Chairman's true intentions are gradually revealed. The series explores themes of identity, belonging, and the meaning of family, as each member grapples with their past and their place within the group.

Throughout the series, the family faces various challenges, both internal and external, including rival factions, personal conflicts, and the consequences of their own actions. The dynamic between the characters evolves as they grow closer, forming genuine bonds despite their initial reluctance. The blend of humor, action, and emotional depth creates a multifaceted narrative that balances lighthearted moments with more serious undertones. "Kyōran Kazoku Nikki" ultimately presents a unique take on the concept of family, blending the absurd with the heartfelt in a way that keeps the audience engaged from start to finish.