A high school student named Kotoko Aihara has spent two years secretly in love with her classmate Naoki Irie, a handsome and effortlessly brilliant student who remains cold and indifferent to everyone around him. Gathering her courage, she finally hands him a love letter, only to have him reject her bluntly in front of the entire school. Humiliated but determined to move on, she tries to forget him, but fate has other plans. That very night, Kotoko’s house is destroyed, either collapsing in an earthquake or burning down depending on the adaptation, leaving her and her father homeless. Her father’s childhood friend graciously offers them a place to stay, and to Kotoko’s shock and horror, that friend is Naoki’s father. She suddenly finds herself living under the same roof as the boy who just broke her heart.

The story is set in modern Tokyo, moving from the halls of their high school to university campuses and eventually into the professional world. Kotoko is cheerful, earnest, and famously at the bottom of her class, consistently struggling with academics. Naoki is her complete opposite; he is a genius who excels at everything without apparent effort, and his personality is distant, sarcastic, and often brutally honest. Living together forces them into an awkward intimacy. Naoki’s mother, Noriko, is a warm and mischievous woman who has always wanted a daughter and immediately adores Kotoko, constantly scheming to push the two young people together. The household also includes Naoki’s quiet, perceptive younger brother, Yuki.

The central narrative arc follows the slow, often painful, evolution of their relationship over several years. Initially, Naoki is annoyed by Kotoko’s presence and her relentless, clumsy efforts to win his affection. Kotoko, for her part, struggles with her feelings as she experiences both his casual cruelty and rare, unexpected moments of kindness. A key early arc involves Kotoko using an embarrassing childhood photo of Naoki to blackmail him into tutoring her so she can try to pass the entrance exam for the prestigious university he plans to attend. Though she fails to get into his school, she eventually passes the exam for a different department at the same university, allowing their paths to remain crossed.

Their dynamic shifts when they enter university, where new rivals appear. A beautiful and skilled tennis player named Yuko Matsumoto takes an interest in Naoki, and Kotoko’s longtime friend and classmate, the kind-hearted but simple Kinnosuke Ikezawa, continues his devoted pursuit of Kotoko. Jealousy becomes a significant force, forcing Naoki to confront his own hidden feelings. A major turning point occurs when Naoki’s father suffers a health crisis, leading Naoki to leave university to take over and revive the struggling family business. This decision shows a more responsible and passionate side of him, deepening Kotoko’s love.

The story continues as Naoki, now a young businessman, is pressured by his mother into an arranged marriage meeting. Believing Kotoko will be better off without him, he agrees to the engagement. Devastated, Kotoko finally accepts Kinnosuke’s long-standing marriage proposal. It is only on the verge of losing her forever that Naoki finally breaks through his emotional walls and publicly declares his love, proposing to Kotoko. The narrative concludes with their wedding, bringing their long, tumultuous journey from a humiliating rejection to a happy marriage to a close.