In a world forever changed by a 1992 pandemic of viral encephalitis, humanity was saved by a revolutionary medical technology that evolved into Your Forma, an invasive information device implanted directly into the brain. In this society, every visual, sound, and even emotion experienced by citizens is recorded, creating a vast sea of collective data. Investigating major crimes now requires diving into these recorded memories, a task reserved for special detectives known as Electronic Investigators.

Petit Forma: Electrocrime Bureau Journal is a spin-off that shifts focus away from the heavy suspense of the main series to offer a relaxed and comedic look at the daily lives of its characters. The story centers on the super-deformed, or SD, versions of the brilliant but isolated Electronic Investigator prodigy Echika Hieda and her new partner, a blonde, blue-eyed android named Harold W. Lucraft, who belongs to the Amicus series of humanoids. Their dynamic as an unrivaled investigative duo is re-imagined in lighter, everyday situations within their workplace, the Electrocrime Bureau.

The mini-anime follows Echika and Harold alongside other members of the bureau, including their colleagues Bigga, Totoki, and Fokine, as they navigate small-scale misadventures and office interactions. Unlike the main narrative, which focuses on intricate cyber-crime cases and deep dives into suspects' memories, Petit Forma focuses on character-driven comedy and slice-of-life scenarios. The notable narrative arc is not a single case but a continuous, episodic presentation of the characters' off-duty moments and the humorous side of their professional relationships, contrasting sharply with the high-stakes technological thriller that defines the original story.