"Ikari no Okorizaru Kansatsu Nikki" is a psychological drama that explores the complexities of human behavior and societal norms through the lens of a unique experiment. The narrative centers around a group of researchers who conduct an observational study on a man referred to as "Okorizaru," a volatile individual prone to extreme outbursts of anger. The researchers isolate Okorizaru in a controlled environment, monitoring his reactions to various stimuli to understand the root causes of his rage and its impact on those around him.

The story unfolds through the perspective of the researchers, who document Okorizaru's behavior in detailed observation logs. As the experiment progresses, the line between observer and subject begins to blur. The researchers find themselves increasingly affected by Okorizaru's unpredictable actions, raising questions about the ethics of their study and the nature of human empathy. The narrative delves into themes of control, morality, and the consequences of isolating individuals from societal norms.

Key characters include the lead researcher, who serves as the primary narrator, and Okorizaru himself, whose backstory and motivations are gradually revealed. The supporting cast consists of other researchers and staff involved in the experiment, each contributing to the unfolding drama through their interactions with Okorizaru and their own personal struggles. The series maintains a tense atmosphere, with moments of psychological intensity as the experiment spirals into unforeseen territory.

The plot is driven by the escalating tension between Okorizaru and the researchers, culminating in a series of dramatic confrontations that challenge the boundaries of the experiment. The narrative does not shy away from exploring the darker aspects of human nature, presenting a thought-provoking examination of anger, isolation, and the ethical dilemmas inherent in scientific observation. The series concludes with an ambiguous resolution, leaving viewers to reflect on the implications of the experiment and its impact on all involved.