Akito Oota is a high school boy whose every thought and emotion broadcasts itself across his face in an instant. His classmate, Hiyori Kashiwada, is his complete opposite: a girl whose expression never changes, leaving her perpetually unreadable. Intrigued and somewhat annoyed by her stoic mask, Oota makes it his mission to crack it, devising a constant stream of pranks and scares designed to finally make her flinch, laugh, or scream. However, his schemes inevitably fail because Kashiwada can read his intentions as easily as a billboard on his overly expressive face. Unbeknownst to Oota, his efforts are not in vain; Kashiwada does have a rich inner world of emotions and has actually held a secret crush on him since they were children in kindergarten together. While her face remains a perfect poker visage, her genuine feelings are often revealed to the audience through subtle cues or small physical gestures.

The story is set in a modern Japanese high school, where the daily routine of classes, holidays, and school events provides the backdrop for the pair's unusual relationship. The core of the series revolves around the comedic and heartwarming dynamic that develops as Oota’s loud, often clumsy attempts to get a reaction out of Kashiwada are misinterpreted by their friends and teachers. The class president, Tabuchi, sees Oota as a bully and positions herself as Kashiwada’s protective fan. Oota’s friends, the easy-going Tadokoro and the calm Sata, often act as commentators on the duo's antics. A significant shift occurs with the introduction of Odajima, a new classmate who possesses a unique ability to read the subtle shifts in Kashiwada’s normally blank expression, adding a new layer to their interactions.

Several notable narrative arcs drive the series forward. An early arc explores a flashback to their kindergarten days, revealing the origin of Kashiwada’s feelings and a forgotten promise that adds emotional weight to Oota’s seemingly thoughtless pranks. Another key arc involves a chaotic beach trip where Oota’s mischievous older sister arrives to meddle, seeing through his denial and actively trying to push the two together. Conversely, an arc where Kashiwada falls ill leads to an encounter with her doting but equally inexpressive older brother, who is fiercely protective and suspicious of Oota’s intentions. The series also follows standard school-life milestones through this unique lens, including a Valentine’s Day arc where the pressure of giving chocolate forces both characters to confront their unspoken feelings, and a summer festival finale that serves as a culmination of their slowly growing bond. Throughout these events, Oota’s initial goal shifts from simply wanting to see a reaction to genuinely caring for Kashiwada, even as he struggles to express his own affection without the veil of a prank.