The story picks up with Tooyama Yukiya, a socially awkward high school student, finding himself in a predicament. He receives a note from Saeki Naru, a classmate he secretly admires, asking him to meet her on the rooftop after school for something important. Yukiya, aware of his low social standing and the bullying he endures from the school's popular "gal trio" (Tanaka, Sato, and Takahashi), suspects this is a trap, likely a prank orchestrated by the girls. He believes Naru, a quiet, bespectacled girl with a hidden beauty, is being forced to participate.
On the rooftop, Naru, visibly nervous, confesses her feelings for Yukiya, stating she's liked him since their first year. Yukiya, convinced this is a setup, accepts her confession to protect her pride and avoid further humiliation. However, his acceptance prolongs the "game," much to his dismay. Naru, overjoyed, begins calling him by his first name, "Yukiya-kun," which deeply affects him. He reciprocates by calling her "Naru," and tears well up in his eyes, not from happiness, but from the realization that his peaceful school life is over. Naru, misinterpreting his tears as joy, reassures him.
Later, Naru reveals that the confession was indeed part of a plan, but insists it was her idea, with the gal trio's support. Yukiya is relieved she wasn't the sole instigator. As they walk home, Yukiya learns that Naru's interest in him stems from several small acts of kindness he performed in his first year, which she observed and admired. He's disturbed by the extent of the girls' surveillance and planning. Naru, who lives in a luxurious apartment, suggests they walk home together, and Yukiya, despite his anxiety, holds her hand, a gesture that further intensifies his internal turmoil.
Back home, Yukiya's younger sister, Akina, notices his distress. He deflects her questions, trying to shield his family from his predicament. Later, he receives a LINE message from Naru, initiating their "relationship." He responds with a deliberately awkward and "creepy" message, hoping to hasten the end of the prank.
The next morning, Naru arrives at Yukiya's house to walk him to school. His sister, Akina, is shocked by Naru's beauty and Yukiya's sudden relationship. Naru explains they started dating yesterday, and Akina, despite her initial surprise, earnestly asks Naru to take care of her brother. Akina is puzzled by Yukiya's subdued reaction to dating such a beautiful girl, suspecting something is wrong.
As they walk to school, Naru asks Yukiya to hold her hand again, and he complies, though hesitantly. They are intercepted by Tanaka Hana, one of the gal trio, who taunts them. Yukiya, overwhelmed, squeezes Naru's hand too tightly, causing her pain. Tanaka leaves, but Yukiya is consumed by dread.
At school, Yukiya's only friend, Hattori Shuzo, confronts him about holding hands with Naru, accusing him of breaking their "oath of being unpopular." Yukiya tries to explain it's a misunderstanding, but Hattori is unconvinced. Yukiya's tears of distress are misinterpreted by Hattori and Naru as happiness over their new relationship.
During lunch, Naru invites Yukiya to eat her homemade bento. Yukiya, despite his dread, accepts. Hattori, seeing them together, declines to join, believing he would be intruding on their "newlywed" moment. On the rooftop, Naru offers to feed Yukiya, a gesture that deeply embarrasses him. He accepts, and as he eats the egg roll she offers, he hears a crunch, realizing something is amiss.