The story begins with Minase Eri, an internal transfer student at Private Ousaki Kouhou Gakuen, expressing her profound boredom and sense of isolation. Despite her outwardly cool demeanor, she secretly yearns for change and excitement, particularly hoping that external students might bring a fresh dynamic to her unchanging life.
Concurrently, Kido Souta, an external transfer student, is introduced in a state of panic. He is deeply embarrassed by his middle school past as a "chuunibyou" who believed he could manipulate people using psychological techniques. His primary goal for high school is to completely reset his image and live a quiet, normal life, having specifically chosen this school to avoid anyone from his past. He employs the "Halo Effect" with fake glasses to project an image of seriousness and diligence.
Souta's carefully laid plans quickly unravel on the first day. After saving a girl from falling on the stairs, he is surprised when she calls him by name, hinting at his growing visibility. Upon entering his classroom, he is instantly captivated by the overwhelming beauty and presence of Minase Eri, who is revealed to be the popular "Minase-san" he'd heard about. His self-introduction is complicated by the revelation that he is the *only* external student, drawing unwanted attention, but Eri smoothly intervenes to calm the class.
A battle of wits quickly ensues. Eri challenges Souta to tell her fortune, attempting to assert dominance. Souta, using his knowledge of psychological effects like the "Barnum Effect," "Hot Reading," and "Cold Reading," accurately describes her, impressing the class and Eri herself. Eri then manipulates the situation by nominating Souta for class representative, forcing his hand. In retaliation, Souta nominates Eri, leading to both being selected.
Eri leads Souta to an empty classroom, locks the door, and reveals her true, manipulative, and playful personality. She exposes his "fortune-telling" as a trick, demonstrating her own deep understanding of psychology, and even threatens him if he doesn't cooperate. She proposes a "Mutual Secret Sharing Agreement" (SHKKK) to keep their true selves and shared knowledge secret, establishing a unique, secret bond. Eri constantly teases Souta, enjoying his flustered reactions, and even puts his new bag in a dusty locker. In the auditorium, Eri further demonstrates her manipulative prowess by smoothly lying to a teacher about Souta's class representative selection and later sends him a teasing "kidnapper" email, further disrupting his composure.
After the ceremony, Souta uses the "Labeling Effect" to escape persistent classmates asking for fortune-telling. He attempts to use the back gate to avoid aggressive club recruitment, a new school policy to create "features." However, he gets lost in the complex alleyways and stumbles upon Eri being harassed by two men. He scares off her attackers, but Eri, seizing the opportunity, "punishes" him by forcing him to walk her home. Their walk continues their psychological sparring. Souta tries to avoid being seen with her to prevent rumors, but Eri insists on walking with him, claiming their paths are merely coincidental. She dismisses his concerns and continues to tease him, enjoying his "tsukkomi" reactions, even calling him the "root of all evil" for bringing out her playful "boke" side. The chapter concludes with Eri getting genuinely annoyed that Souta calls her "omae" instead of "Minase-san" when they are alone, expressing her frustration with an exaggerated internet meme, leaving Souta bewildered and looking it up on his phone.
From Eri's initial boredom and Souta's desire for anonymity, their lives have become inextricably linked. Souta's carefully constructed facade has been shattered by Eri's perceptive and playful manipulation, and his goal of a quiet high school life has been replaced by a dynamic, exasperating, yet intriguing relationship with the school's most popular and manipulative girl.
