Kouichi Sakakibara is the male protagonist of the story, a thoughtful and observant middle school student who transfers to Yomiyama North Middle School at the start of the third term. He has spent much of his childhood in a hospital due to a chronic pneumothorax, a condition that has left him somewhat isolated and introspective. Because of his illness, he has not formed lasting friendships or participated in normal school life, which makes him both curious about social connections and slightly awkward in his interactions. His family background is marked by loss: his mother died of an illness when he was young, and his father works abroad as a researcher, leaving Kouichi to live temporarily with his maternal grandparents in the town of Yomiyama.

Personality wise, Kouichi is calm, polite, and analytical, with a natural inclination to question things that do not make logical sense. He is not easily swayed by fear or peer pressure, and he treats others with consistent respect even when they act coldly or strangely. Beneath his composed exterior, he is deeply compassionate and driven by a desire to understand the truth behind the mysterious deaths plaguing his new class, as well as to help the people he cares about. He can be stubborn once he commits to a course of action, especially when he believes that ignoring a problem is equivalent to accepting needless tragedy. His time in hospitals has also made him patient and observant, noticing small details that others might overlook.

Kouichi’s primary motivation is to uncover the nature of the calamity that affects his class, known as Class 3. Shortly after arriving, he learns that the class is under a curse that causes students, their immediate family members, and sometimes close relatives to die gruesome, accidental deaths at an alarming rate. The only known method to halt the deaths is for the class to collectively pretend that a certain deceased student continues to live among them, a practice that has been in place for decades. Kouichi refuses to accept this passive solution, believing that addressing the identity of the extra student, the one who has supposedly returned from the dead, is the only way to end the curse permanently. His motivation is partly personal: he has already lost his mother and a younger sister he never knew, and he cannot bear to lose new friends like Mei Misaki without fighting back.

In the story’s progression, Kouichi serves as the central investigator and emotional anchor. He is the one who actively seeks information about the curse’s origin, the identity of the dead student, and the rules that govern the phenomenon. While other students and adults in the town are aware of the curse, most choose to follow the tradition of ignoring the extra person out of fear. Kouichi’s refusal to comply with this silence makes him a disruptive force in the class, but it also drives the plot toward its resolution. His role is not that of a hero in the conventional sense; he rarely fights or takes physical action, but his determination to face the truth head on eventually forces the curse to escalate and reveal itself.

Key relationships shape much of his development. His bond with Mei Misaki, the quiet, eye-patched girl whom the rest of the class pretends does not exist, is the most significant. Initially, he is drawn to her because she alone acknowledges the abnormality of the class’s behavior. Their friendship forms the emotional core of the story: she provides him with crucial knowledge about the curse, including the existence of the deceased student, and he gives her the human connection she has been denied. Kouichi also interacts with several classmates, such as Tomohiko Kazami, the class representative who tries to maintain the fragile peace by enforcing the policy of ignoring Mei, and Naoya Teshigawara, a loud and friendly student who becomes an ally. His relationships with his grandparents, particularly his grandmother who is affected by dementia, add a layer of domestic tension and foreshadowing. Finally, his connection to Reiko Mikami, the class’s homeroom teacher, takes a tragic turn when it is revealed that she is the dead student, a fact that Kouichi uncovers through patient deduction.

Over the course of the story, Kouichi undergoes significant development. He enters Yomiyama as a passive observer, someone whose illness kept him on the sidelines of life. By the end, he has become an active agent, willing to confront terror and loss directly. His initial belief that logic and communication can solve any problem is tested when the curse proves to operate on seemingly irrational, supernatural rules. He learns that some truths are painful and that seeking them can cause more immediate suffering than ignoring them. However, he does not abandon his principles; rather, he accepts that responsibility for others sometimes requires taking risks that may lead to disaster. The trauma he witnesses, including multiple deaths and the near death of Mei, hardens his resolve but does not make him cynical. By the conclusion, he has integrated his lonely past with a newfound capacity for meaningful connection, having finally experienced both friendship and the courage to face what others flee.

Notable abilities of Kouichi Sakakibara include his sharp observational skills and deductive reasoning. He is able to piece together clues from seemingly unrelated events, such as the pattern of deaths, the significance of the doll Mei carries, and the inconsistencies in the class’s records. He also has a high tolerance for psychological stress, remaining functional and clear headed even when people die violently around him. While he has no combat skills or supernatural powers, his persistence and willingness to ask forbidden questions make him the catalyst that breaks the curse’s cycle. His chronic illness is a plot element as well: his collapsed lung occasionally recurs under stress, reminding the audience of his physical vulnerability even as he pushes forward emotionally. Ultimately, his most defining ability is his refusal to look away from the truth, a quality that both endangers and redeems him.